diff --git a/README.md b/README.md
index de6a0096..02c730b2 100644
--- a/README.md
+++ b/README.md
@@ -28,11 +28,11 @@ analysis and unit/quantity manipulation. The basic idea and design heavily bases
 Here is a small example of possible operations:
 
 ```cpp
-#include <units/physical/si/area.h>
-#include <units/physical/si/frequency.h>
-#include <units/physical/si/speed.h>
+#include <units/isq/si/area.h>
+#include <units/isq/si/frequency.h>
+#include <units/isq/si/speed.h>
 
-using namespace units::physical::si;
+using namespace units::isq::si;
 
 // simple numeric operations
 static_assert(10_q_km / 2 == 5_q_km);
@@ -62,12 +62,12 @@ the below example for a quick preview of basic library features:
 
 ```cpp
 #include <units/format.h>
-#include <units/physical/si/speed.h>
-#include <units/physical/si/international/speed.h>
+#include <units/isq/si/speed.h>
+#include <units/isq/si/international/speed.h>
 #include <units/quantity_io.h>
 #include <iostream>
 
-using namespace units::physical;
+using namespace units::isq;
 
 constexpr Speed auto avg_speed(Length auto d, Time auto t)
 {
@@ -76,8 +76,8 @@ constexpr Speed auto avg_speed(Length auto d, Time auto t)
 
 int main()
 {
-  using namespace units::physical::si::literals;
-  using namespace units::physical::si::unit_constants;
+  using namespace units::isq::si::literals;
+  using namespace units::isq::si::unit_constants;
 
   constexpr Speed auto v1 = 110 * km / h;
   constexpr Speed auto v2 = avg_speed(220_q_km, 2_q_h);
diff --git a/docs/CMakeLists.txt b/docs/CMakeLists.txt
index 0b1d18d1..b830eb1e 100644
--- a/docs/CMakeLists.txt
+++ b/docs/CMakeLists.txt
@@ -124,104 +124,104 @@ set(unitsSphinxDocs
     "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/generic/dimensionless.rst"
     "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/generic/unknown.rst"
 
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq.rst"
 
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/natural.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/natural/constants.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/natural/dimensions.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/natural/units.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/natural.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/natural/constants.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/natural/dimensions.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/natural/units.rst"
 
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si_cgs.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/cgs/length.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/cgs/acceleration.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/cgs/area.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/cgs/energy.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/cgs/force.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/cgs/length.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/cgs/mass.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/cgs/power.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/cgs/pressure.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/cgs/speed.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/cgs/time.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si_cgs.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/cgs/length.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/cgs/acceleration.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/cgs/area.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/cgs/energy.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/cgs/force.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/cgs/length.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/cgs/mass.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/cgs/power.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/cgs/pressure.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/cgs/speed.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/cgs/time.rst"
 
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/dimensions_and_concepts.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/dimensions_and_concepts.rst"
 
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si_fps.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/fps/length.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/fps/acceleration.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/fps/area.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/fps/density.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/fps/energy.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/fps/force.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/fps/length.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/fps/mass.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/fps/power.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/fps/pressure.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/fps/speed.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/fps/time.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/fps/volume.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si_fps.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/fps/length.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/fps/acceleration.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/fps/area.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/fps/density.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/fps/energy.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/fps/force.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/fps/length.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/fps/mass.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/fps/power.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/fps/pressure.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/fps/speed.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/fps/time.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/fps/volume.rst"
 
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si_iau.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/iau/length.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si_iau.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/iau/length.rst"
 
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si_imperial.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/imperial/length.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si_imperial.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/imperial/length.rst"
 
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si_international.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/international/area.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/international/length.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/international/speed.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/international/volume.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si_international.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/international/area.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/international/length.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/international/speed.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/international/volume.rst"
 
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/absorbed_dose.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/acceleration.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/amount_of_substance.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/area.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/capacitance.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/catalytic_activity.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/charge_density.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/concentration.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/conductance.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/constants.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/current_density.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/density.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/dynamic_viscosity.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/electric_charge.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/electric_current.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/electric_field_strength.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/energy.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/force.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/frequency.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/heat_capacity.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/inductance.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/length.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/luminance.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/luminous_intensity.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/magnetic_flux.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/magnetic_induction.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/mass.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/molar_energy.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/momentum.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/permeability.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/permittivity.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/power.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/prefixes.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/pressure.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/resistance.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/speed.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/surface_tension.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/thermal_conductivity.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/thermodynamic_temperature.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/time.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/voltage.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/volume.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/absorbed_dose.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/acceleration.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/amount_of_substance.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/area.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/capacitance.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/catalytic_activity.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/charge_density.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/concentration.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/conductance.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/constants.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/current_density.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/density.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/dynamic_viscosity.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/electric_charge.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/electric_current.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/electric_field_strength.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/energy.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/force.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/frequency.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/heat_capacity.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/inductance.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/length.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/luminance.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/luminous_intensity.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/magnetic_flux.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/magnetic_induction.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/mass.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/molar_energy.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/momentum.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/permeability.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/permittivity.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/power.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/prefixes.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/pressure.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/resistance.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/speed.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/surface_tension.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/thermal_conductivity.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/thermodynamic_temperature.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/time.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/voltage.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/volume.rst"
 
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si_typographic.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/typographic/length.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si_typographic.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/typographic/length.rst"
 
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si_us.rst"
-    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/physical/si/us/length.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si_us.rst"
+    "${CMAKE_CURRENT_SOURCE_DIR}/reference/systems/isq/si/us/length.rst"
 
     "${CMAKE_CURRENT_SOURCE_DIR}/references.rst"
 
diff --git a/docs/design.rst b/docs/design.rst
index 1f79773d..0c379c38 100644
--- a/docs/design.rst
+++ b/docs/design.rst
@@ -6,7 +6,7 @@ Design Deep Dive
     For brevity all the code examples in this chapter assume::
 
         using namespace units;
-        using namespace units::physical;
+        using namespace units::isq;
 
 .. toctree::
     :maxdepth: 2
diff --git a/docs/design/directories.rst b/docs/design/directories.rst
index 77b121cc..4f7a6703 100644
--- a/docs/design/directories.rst
+++ b/docs/design/directories.rst
@@ -63,4 +63,4 @@ Library Directories Structure
 
     While working with predefined systems please always include a header file with all
     the definitions for the current system to limit the possibility of an ODR violation
-    (e.g. *units/physical/si/si.h*).
+    (e.g. *units/isq/si/si.h*).
diff --git a/docs/design/downcasting.rst b/docs/design/downcasting.rst
index 13cd66fa..c804c5c5 100644
--- a/docs/design/downcasting.rst
+++ b/docs/design/downcasting.rst
@@ -23,9 +23,9 @@ The above solution does provide a good developer's experience but a really poor
 user. If we will get a compilation error message containing ``dim_capacitance`` in most cases
 the compiler will print the following type instead of the alias::
 
-    units::detail::derived_dimension_base<units::exponent<units::physical::si::dim_electric_current, 2, 1>,
-    units::exponent<units::physical::si::dim_length, -2, 1>, units::exponent<units::physical::si::dim_mass,
-    -1, 1>, units::exponent<units::physical::si::dim_time, 4, 1> >
+    units::detail::derived_dimension_base<units::exponent<units::isq::si::dim_electric_current, 2, 1>,
+    units::exponent<units::isq::si::dim_length, -2, 1>, units::exponent<units::isq::si::dim_mass,
+    -1, 1>, units::exponent<units::isq::si::dim_time, 4, 1> >
 
 You can notice that in case of **mp-units** even this long syntax was carefully selected to
 provide quite good user experience (some other units libraries produce a type that cannot easily
diff --git a/docs/faq.rst b/docs/faq.rst
index e2836e49..d1784c86 100644
--- a/docs/faq.rst
+++ b/docs/faq.rst
@@ -30,10 +30,10 @@ different dimensions (i.e. height, width, and depth) all of them will just be
 measured in meters.
 
 
-Why other systems are defined in the `physical::si` namespace?
+Why other systems are defined in the `isq::si` namespace?
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-All systems defined in the `physical::si` namespace are defined in terms of
+All systems defined in the `isq::si` namespace are defined in terms of
 base units that are convertible to the :term:`SI` units. This enables conversions
 of units of the same physical dimension between different systems.
 
@@ -125,7 +125,7 @@ error: reference to ‘time’ is ambiguous
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 Unfortunately, if `using-directives <https://en.cppreference.com/w/cpp/language/namespace#Using-directives>`_
-(i.e. ``using namespace units::physical::si``) are being used, `units::physical::si::time`
+(i.e. ``using namespace units::isq::si``) are being used, `units::isq::si::time`
 will collide with C `time <https://en.cppreference.com/w/c/chrono/time>`_ function. In
 such a case the library's ``time`` function needs to be prefixed with at least one (or all)
 namespace names.
diff --git a/docs/framework.rst b/docs/framework.rst
index 1c94f436..494f7150 100644
--- a/docs/framework.rst
+++ b/docs/framework.rst
@@ -6,7 +6,7 @@ Framework Basics
     For brevity all the code examples in this chapter assume::
 
         using namespace units;
-        using namespace units::physical;
+        using namespace units::isq;
 
 .. toctree::
     :maxdepth: 2
diff --git a/docs/framework/dimensions.rst b/docs/framework/dimensions.rst
index d81c8258..46dbc83b 100644
--- a/docs/framework/dimensions.rst
+++ b/docs/framework/dimensions.rst
@@ -171,7 +171,7 @@ provided. For example the SI base dimension of length can be defined as::
     }
 
 In the above code sample ``"L"`` is an base dimension's unique identifier
-and `physical::si::metre` is a :term:`base unit` of this base dimension. We can
+and `isq::si::metre` is a :term:`base unit` of this base dimension. We can
 obtain those back easily with::
 
     static_assert(si::dim_length::symbol == "L");
@@ -206,8 +206,8 @@ The above dimensions can be defined in the library with the
 
     }
 
-In the above code sample `physical::si::square_metre` and
-`physical::si::metre_per_second` are the
+In the above code sample `isq::si::square_metre` and
+`isq::si::metre_per_second` are the
 :term:`coherent derived units <coherent derived unit>` of those derived dimensions.
 
 Coherent unit argument is followed by the list of exponents that form this
diff --git a/docs/framework/quantities.rst b/docs/framework/quantities.rst
index 0204984e..f7003143 100644
--- a/docs/framework/quantities.rst
+++ b/docs/framework/quantities.rst
@@ -69,7 +69,7 @@ values the library provides :abbr:`UDL (User Defined Literal)` s for each
 
 Thanks to them the same code can be as simple as::
 
-    using namespace units::physical::si::literals;
+    using namespace units::isq::si::literals;
     auto d = 123._q_km;     // si::length<si::kilometre, long double>
     auto v = 70_q_km_per_h; // si::speed<si::kilometre_per_hour, std::int64_t>
 
@@ -98,7 +98,7 @@ They are defined using a special `one_rep` representation type::
 
 With the above our code can look as follows::
 
-    using namespace units::physical::si::unit_constants;
+    using namespace units::isq::si::unit_constants;
     auto d = 123. * km;     // si::length<si::kilometre, double>
     auto v = 70 * km / h;   // si::speed<si::kilometre_per_hour, int>
 
@@ -121,13 +121,13 @@ UDLs are helpful but they also have some disadvantages compared to Unit Constant
 
    - UDLs::
 
-       using namespace units::physical::si::literals;
+       using namespace units::isq::si::literals;
        auto v1 = 120_q_km / 2_q_h;
        auto v2 = length<kilometre>(distance) / time<hour>(duration);
 
    - Unit Constants::
 
-       using namespace units::physical::si::unit_constants;
+       using namespace units::isq::si::unit_constants;
        auto v1 = 120 * km / (2 * h);
        auto v2 = distance * km / (duration * h);
 
@@ -139,14 +139,14 @@ UDLs are helpful but they also have some disadvantages compared to Unit Constant
 
    - UDLs::
 
-       using namespace units::physical::si::literals;
-       using namespace units::physical::si::cgs::literals;
+       using namespace units::isq::si::literals;
+       using namespace units::isq::si::cgs::literals;
        auto d = 1_q_cm;   // FAILS TO COMPILE
 
    - Unit Constants::
 
-       inline constexpr auto si_cm = units::physical::si::unit_constants::cm;
-       inline constexpr auto cgs_cm = units::physical::si::cgs::unit_constants::cm;
+       inline constexpr auto si_cm = units::isq::si::unit_constants::cm;
+       inline constexpr auto cgs_cm = units::isq::si::cgs::unit_constants::cm;
 
        auto d1 = 1. * si_cm;   // si::length<si::centimetre>
        auto d2 = 1. * cgs_cm;  // si::cgs::length<si::centimetre>
@@ -156,7 +156,7 @@ UDLs are helpful but they also have some disadvantages compared to Unit Constant
 
    - UDLs::
 
-       using namespace units::physical::si::literals;
+       using namespace units::isq::si::literals;
        auto d1 = 123._q_km;   // si::length<si::kilometre, long double>
        auto d2 = 123_q_km;    // si::length<si::kilometre, std::int64_t>
 
@@ -164,7 +164,7 @@ UDLs are helpful but they also have some disadvantages compared to Unit Constant
 
    - Unit Constants::
 
-       using namespace units::physical::si::unit_constants;
+       using namespace units::isq::si::unit_constants;
        auto d1 = 123. * km;   // si::length<si::kilometre, double>
        auto d2 = 123 * km;    // si::length<si::kilometre, int>
        auto d3 = 123.f * km;  // si::length<si::kilometre, float>
@@ -194,7 +194,7 @@ UDLs are helpful but they also have some disadvantages compared to Unit Constant
 The only issue we are aware of with Unit Constants is a potential problem of specifying
 a quantity in denominator::
 
-    using namespace units::physical::si::unit_constants;
+    using namespace units::isq::si::unit_constants;
     Speed auto v = 220 * km / 2 * h;  // FAILS TO COMPILE (not a quantity of a speed dimension)
 
 The above code can be fixed in one of the below ways:
@@ -220,7 +220,7 @@ In case the user does not care about the specific unit and representation but
 requires quantity of a concrete dimension than dimension-specific concepts can
 be used::
 
-    using namespace units::physical::si::literals;
+    using namespace units::isq::si::literals;
     constexpr Length auto d = 123_q_km;  // si::length<si::kilometre, std::int64_t>
 
 .. note::
@@ -235,8 +235,8 @@ assume that the user wants to implement an ``avg_speed`` function that will
 be calculating the average speed based on provided distance and duration
 quantities. The usage of such a function can look as follows::
 
-    using namespace units::physical::si::literals;
-    using namespace units::physical::si::international::literals;
+    using namespace units::isq::si::literals;
+    using namespace units::isq::si::international::literals;
     constexpr Speed auto v1 = avg_speed(220_q_km, 2_q_h);
     constexpr Speed auto v2 = avg_speed(140_q_mi, 2_q_h);
 
diff --git a/docs/framework/text_output.rst b/docs/framework/text_output.rst
index 678b85fd..45c0c54b 100644
--- a/docs/framework/text_output.rst
+++ b/docs/framework/text_output.rst
@@ -21,8 +21,8 @@ Output Streams
 The easiest way to print a quantity is to provide its object to the output
 stream::
 
-    using namespace units::physical::si::literals;
-    using namespace units::physical::si::international::literals;
+    using namespace units::isq::si::literals;
+    using namespace units::isq::si::international::literals;
     constexpr Speed auto v1 = avg_speed(220._q_km, 2_q_h);
     constexpr Speed auto v2 = avg_speed(140._q_mi, 2_q_h);
     std::cout << v1 << '\n';  // 110 km/h
diff --git a/docs/framework/units.rst b/docs/framework/units.rst
index 6e6adac6..d1449351 100644
--- a/docs/framework/units.rst
+++ b/docs/framework/units.rst
@@ -388,7 +388,7 @@ and user should not instantiate it by him/her-self. However the user can sometim
 observe this type in case an unit/dimension conversion expression will end up with an
 unknown/undefined unit type like in the below example::
 
-    using namespace units::physical::si::literals;
+    using namespace units::isq::si::literals;
 
     Length auto l = 100_q_km_per_h * 10_q_s;
 
diff --git a/docs/quick_start.rst b/docs/quick_start.rst
index 419c2ab1..9155501e 100644
--- a/docs/quick_start.rst
+++ b/docs/quick_start.rst
@@ -3,11 +3,11 @@ Quick Start
 
 Here is a small example of possible operations::
 
-    #include <units/physical/si/area.h>
-    #include <units/physical/si/frequency.h>
-    #include <units/physical/si/speed.h>
+    #include <units/isq/si/area.h>
+    #include <units/isq/si/frequency.h>
+    #include <units/isq/si/speed.h>
 
-    using namespace units::physical::si;
+    using namespace units::isq::si;
 
     // simple numeric operations
     static_assert(10_q_km / 2 == 5_q_km);
@@ -38,12 +38,12 @@ performed without sacrificing on accuracy. Please see the below example for a qu
 of basic library features::
 
     #include <units/format.h>
-    #include <units/physical/si/speed.h>
-    #include <units/physical/si/international/speed.h>
+    #include <units/isq/si/speed.h>
+    #include <units/isq/si/international/speed.h>
     #include <units/quantity_io.h>
     #include <iostream>
 
-    using namespace units::physical;
+    using namespace units::isq;
 
     constexpr Speed auto avg_speed(Length auto d, Time auto t)
     {
@@ -52,8 +52,8 @@ of basic library features::
 
     int main()
     {
-      using namespace units::physical::si::literals;
-      using namespace units::physical::si::unit_constants;
+      using namespace units::isq::si::literals;
+      using namespace units::isq::si::unit_constants;
 
       constexpr Speed auto v1 = 110 * km / h;
       constexpr Speed auto v2 = avg_speed(220_q_km, 2_q_h);
diff --git a/docs/reference/systems.rst b/docs/reference/systems.rst
index aa5ce92b..c8e864ac 100644
--- a/docs/reference/systems.rst
+++ b/docs/reference/systems.rst
@@ -9,7 +9,7 @@ Systems
 .. toctree::
     :maxdepth: 2
 
-    systems/physical
+    systems/isq
 
 .. toctree::
     :maxdepth: 1
diff --git a/docs/reference/systems/physical.rst b/docs/reference/systems/isq.rst
similarity index 76%
rename from docs/reference/systems/physical.rst
rename to docs/reference/systems/isq.rst
index 8faa2480..fe2b6256 100644
--- a/docs/reference/systems/physical.rst
+++ b/docs/reference/systems/isq.rst
@@ -1,5 +1,5 @@
-Physical
-========
+International System of Quantities (ISQ)
+========================================
 
 .. toctree::
     :maxdepth: 2
diff --git a/docs/reference/systems/physical/dimensions_and_concepts.rst b/docs/reference/systems/isq/dimensions_and_concepts.rst
similarity index 100%
rename from docs/reference/systems/physical/dimensions_and_concepts.rst
rename to docs/reference/systems/isq/dimensions_and_concepts.rst
diff --git a/docs/reference/systems/physical/natural.rst b/docs/reference/systems/isq/natural.rst
similarity index 100%
rename from docs/reference/systems/physical/natural.rst
rename to docs/reference/systems/isq/natural.rst
diff --git a/docs/reference/systems/physical/natural/constants.rst b/docs/reference/systems/isq/natural/constants.rst
similarity index 100%
rename from docs/reference/systems/physical/natural/constants.rst
rename to docs/reference/systems/isq/natural/constants.rst
diff --git a/docs/reference/systems/physical/natural/dimensions.rst b/docs/reference/systems/isq/natural/dimensions.rst
similarity index 100%
rename from docs/reference/systems/physical/natural/dimensions.rst
rename to docs/reference/systems/isq/natural/dimensions.rst
diff --git a/docs/reference/systems/physical/natural/units.rst b/docs/reference/systems/isq/natural/units.rst
similarity index 100%
rename from docs/reference/systems/physical/natural/units.rst
rename to docs/reference/systems/isq/natural/units.rst
diff --git a/docs/reference/systems/physical/si.rst b/docs/reference/systems/isq/si.rst
similarity index 92%
rename from docs/reference/systems/physical/si.rst
rename to docs/reference/systems/isq/si.rst
index f3f43239..122fa55f 100644
--- a/docs/reference/systems/physical/si.rst
+++ b/docs/reference/systems/isq/si.rst
@@ -1,5 +1,5 @@
-SI
-==
+International System of Units (SI)
+==================================
 
 .. toctree::
     :maxdepth: 2
diff --git a/docs/reference/systems/physical/si/absorbed_dose.rst b/docs/reference/systems/isq/si/absorbed_dose.rst
similarity index 100%
rename from docs/reference/systems/physical/si/absorbed_dose.rst
rename to docs/reference/systems/isq/si/absorbed_dose.rst
diff --git a/docs/reference/systems/physical/si/acceleration.rst b/docs/reference/systems/isq/si/acceleration.rst
similarity index 100%
rename from docs/reference/systems/physical/si/acceleration.rst
rename to docs/reference/systems/isq/si/acceleration.rst
diff --git a/docs/reference/systems/physical/si/amount_of_substance.rst b/docs/reference/systems/isq/si/amount_of_substance.rst
similarity index 100%
rename from docs/reference/systems/physical/si/amount_of_substance.rst
rename to docs/reference/systems/isq/si/amount_of_substance.rst
diff --git a/docs/reference/systems/physical/si/area.rst b/docs/reference/systems/isq/si/area.rst
similarity index 100%
rename from docs/reference/systems/physical/si/area.rst
rename to docs/reference/systems/isq/si/area.rst
diff --git a/docs/reference/systems/physical/si/capacitance.rst b/docs/reference/systems/isq/si/capacitance.rst
similarity index 100%
rename from docs/reference/systems/physical/si/capacitance.rst
rename to docs/reference/systems/isq/si/capacitance.rst
diff --git a/docs/reference/systems/physical/si/catalytic_activity.rst b/docs/reference/systems/isq/si/catalytic_activity.rst
similarity index 100%
rename from docs/reference/systems/physical/si/catalytic_activity.rst
rename to docs/reference/systems/isq/si/catalytic_activity.rst
diff --git a/docs/reference/systems/physical/si/cgs/acceleration.rst b/docs/reference/systems/isq/si/cgs/acceleration.rst
similarity index 100%
rename from docs/reference/systems/physical/si/cgs/acceleration.rst
rename to docs/reference/systems/isq/si/cgs/acceleration.rst
diff --git a/docs/reference/systems/physical/si/cgs/area.rst b/docs/reference/systems/isq/si/cgs/area.rst
similarity index 100%
rename from docs/reference/systems/physical/si/cgs/area.rst
rename to docs/reference/systems/isq/si/cgs/area.rst
diff --git a/docs/reference/systems/physical/si/cgs/energy.rst b/docs/reference/systems/isq/si/cgs/energy.rst
similarity index 100%
rename from docs/reference/systems/physical/si/cgs/energy.rst
rename to docs/reference/systems/isq/si/cgs/energy.rst
diff --git a/docs/reference/systems/physical/si/cgs/force.rst b/docs/reference/systems/isq/si/cgs/force.rst
similarity index 100%
rename from docs/reference/systems/physical/si/cgs/force.rst
rename to docs/reference/systems/isq/si/cgs/force.rst
diff --git a/docs/reference/systems/physical/si/cgs/length.rst b/docs/reference/systems/isq/si/cgs/length.rst
similarity index 100%
rename from docs/reference/systems/physical/si/cgs/length.rst
rename to docs/reference/systems/isq/si/cgs/length.rst
diff --git a/docs/reference/systems/physical/si/cgs/mass.rst b/docs/reference/systems/isq/si/cgs/mass.rst
similarity index 100%
rename from docs/reference/systems/physical/si/cgs/mass.rst
rename to docs/reference/systems/isq/si/cgs/mass.rst
diff --git a/docs/reference/systems/physical/si/cgs/power.rst b/docs/reference/systems/isq/si/cgs/power.rst
similarity index 100%
rename from docs/reference/systems/physical/si/cgs/power.rst
rename to docs/reference/systems/isq/si/cgs/power.rst
diff --git a/docs/reference/systems/physical/si/cgs/pressure.rst b/docs/reference/systems/isq/si/cgs/pressure.rst
similarity index 100%
rename from docs/reference/systems/physical/si/cgs/pressure.rst
rename to docs/reference/systems/isq/si/cgs/pressure.rst
diff --git a/docs/reference/systems/physical/si/cgs/speed.rst b/docs/reference/systems/isq/si/cgs/speed.rst
similarity index 100%
rename from docs/reference/systems/physical/si/cgs/speed.rst
rename to docs/reference/systems/isq/si/cgs/speed.rst
diff --git a/docs/reference/systems/physical/si/cgs/time.rst b/docs/reference/systems/isq/si/cgs/time.rst
similarity index 100%
rename from docs/reference/systems/physical/si/cgs/time.rst
rename to docs/reference/systems/isq/si/cgs/time.rst
diff --git a/docs/reference/systems/physical/si/charge_density.rst b/docs/reference/systems/isq/si/charge_density.rst
similarity index 100%
rename from docs/reference/systems/physical/si/charge_density.rst
rename to docs/reference/systems/isq/si/charge_density.rst
diff --git a/docs/reference/systems/physical/si/concentration.rst b/docs/reference/systems/isq/si/concentration.rst
similarity index 100%
rename from docs/reference/systems/physical/si/concentration.rst
rename to docs/reference/systems/isq/si/concentration.rst
diff --git a/docs/reference/systems/physical/si/conductance.rst b/docs/reference/systems/isq/si/conductance.rst
similarity index 100%
rename from docs/reference/systems/physical/si/conductance.rst
rename to docs/reference/systems/isq/si/conductance.rst
diff --git a/docs/reference/systems/physical/si/constants.rst b/docs/reference/systems/isq/si/constants.rst
similarity index 100%
rename from docs/reference/systems/physical/si/constants.rst
rename to docs/reference/systems/isq/si/constants.rst
diff --git a/docs/reference/systems/physical/si/current_density.rst b/docs/reference/systems/isq/si/current_density.rst
similarity index 100%
rename from docs/reference/systems/physical/si/current_density.rst
rename to docs/reference/systems/isq/si/current_density.rst
diff --git a/docs/reference/systems/physical/si/density.rst b/docs/reference/systems/isq/si/density.rst
similarity index 100%
rename from docs/reference/systems/physical/si/density.rst
rename to docs/reference/systems/isq/si/density.rst
diff --git a/docs/reference/systems/physical/si/dynamic_viscosity.rst b/docs/reference/systems/isq/si/dynamic_viscosity.rst
similarity index 100%
rename from docs/reference/systems/physical/si/dynamic_viscosity.rst
rename to docs/reference/systems/isq/si/dynamic_viscosity.rst
diff --git a/docs/reference/systems/physical/si/electric_charge.rst b/docs/reference/systems/isq/si/electric_charge.rst
similarity index 100%
rename from docs/reference/systems/physical/si/electric_charge.rst
rename to docs/reference/systems/isq/si/electric_charge.rst
diff --git a/docs/reference/systems/physical/si/electric_current.rst b/docs/reference/systems/isq/si/electric_current.rst
similarity index 100%
rename from docs/reference/systems/physical/si/electric_current.rst
rename to docs/reference/systems/isq/si/electric_current.rst
diff --git a/docs/reference/systems/physical/si/electric_field_strength.rst b/docs/reference/systems/isq/si/electric_field_strength.rst
similarity index 100%
rename from docs/reference/systems/physical/si/electric_field_strength.rst
rename to docs/reference/systems/isq/si/electric_field_strength.rst
diff --git a/docs/reference/systems/physical/si/energy.rst b/docs/reference/systems/isq/si/energy.rst
similarity index 100%
rename from docs/reference/systems/physical/si/energy.rst
rename to docs/reference/systems/isq/si/energy.rst
diff --git a/docs/reference/systems/physical/si/force.rst b/docs/reference/systems/isq/si/force.rst
similarity index 100%
rename from docs/reference/systems/physical/si/force.rst
rename to docs/reference/systems/isq/si/force.rst
diff --git a/docs/reference/systems/physical/si/fps/acceleration.rst b/docs/reference/systems/isq/si/fps/acceleration.rst
similarity index 100%
rename from docs/reference/systems/physical/si/fps/acceleration.rst
rename to docs/reference/systems/isq/si/fps/acceleration.rst
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similarity index 100%
rename from docs/reference/systems/physical/si/fps/area.rst
rename to docs/reference/systems/isq/si/fps/area.rst
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similarity index 100%
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similarity index 100%
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similarity index 100%
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rename to docs/reference/systems/isq/si/fps/force.rst
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rename to docs/reference/systems/isq/si/fps/pressure.rst
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diff --git a/docs/reference/systems/physical/si/frequency.rst b/docs/reference/systems/isq/si/frequency.rst
similarity index 100%
rename from docs/reference/systems/physical/si/frequency.rst
rename to docs/reference/systems/isq/si/frequency.rst
diff --git a/docs/reference/systems/physical/si/heat_capacity.rst b/docs/reference/systems/isq/si/heat_capacity.rst
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diff --git a/docs/reference/systems/physical/si/iau/length.rst b/docs/reference/systems/isq/si/iau/length.rst
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diff --git a/docs/reference/systems/physical/si/imperial/length.rst b/docs/reference/systems/isq/si/imperial/length.rst
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rename from docs/reference/systems/physical/si/pressure.rst
rename to docs/reference/systems/isq/si/pressure.rst
diff --git a/docs/reference/systems/physical/si/resistance.rst b/docs/reference/systems/isq/si/resistance.rst
similarity index 100%
rename from docs/reference/systems/physical/si/resistance.rst
rename to docs/reference/systems/isq/si/resistance.rst
diff --git a/docs/reference/systems/physical/si/speed.rst b/docs/reference/systems/isq/si/speed.rst
similarity index 100%
rename from docs/reference/systems/physical/si/speed.rst
rename to docs/reference/systems/isq/si/speed.rst
diff --git a/docs/reference/systems/physical/si/surface_tension.rst b/docs/reference/systems/isq/si/surface_tension.rst
similarity index 100%
rename from docs/reference/systems/physical/si/surface_tension.rst
rename to docs/reference/systems/isq/si/surface_tension.rst
diff --git a/docs/reference/systems/physical/si/thermal_conductivity.rst b/docs/reference/systems/isq/si/thermal_conductivity.rst
similarity index 100%
rename from docs/reference/systems/physical/si/thermal_conductivity.rst
rename to docs/reference/systems/isq/si/thermal_conductivity.rst
diff --git a/docs/reference/systems/physical/si/thermodynamic_temperature.rst b/docs/reference/systems/isq/si/thermodynamic_temperature.rst
similarity index 100%
rename from docs/reference/systems/physical/si/thermodynamic_temperature.rst
rename to docs/reference/systems/isq/si/thermodynamic_temperature.rst
diff --git a/docs/reference/systems/physical/si/time.rst b/docs/reference/systems/isq/si/time.rst
similarity index 100%
rename from docs/reference/systems/physical/si/time.rst
rename to docs/reference/systems/isq/si/time.rst
diff --git a/docs/reference/systems/physical/si/typographic/length.rst b/docs/reference/systems/isq/si/typographic/length.rst
similarity index 100%
rename from docs/reference/systems/physical/si/typographic/length.rst
rename to docs/reference/systems/isq/si/typographic/length.rst
diff --git a/docs/reference/systems/physical/si/us/length.rst b/docs/reference/systems/isq/si/us/length.rst
similarity index 100%
rename from docs/reference/systems/physical/si/us/length.rst
rename to docs/reference/systems/isq/si/us/length.rst
diff --git a/docs/reference/systems/physical/si/voltage.rst b/docs/reference/systems/isq/si/voltage.rst
similarity index 100%
rename from docs/reference/systems/physical/si/voltage.rst
rename to docs/reference/systems/isq/si/voltage.rst
diff --git a/docs/reference/systems/physical/si/volume.rst b/docs/reference/systems/isq/si/volume.rst
similarity index 100%
rename from docs/reference/systems/physical/si/volume.rst
rename to docs/reference/systems/isq/si/volume.rst
diff --git a/docs/reference/systems/physical/si_cgs.rst b/docs/reference/systems/isq/si_cgs.rst
similarity index 100%
rename from docs/reference/systems/physical/si_cgs.rst
rename to docs/reference/systems/isq/si_cgs.rst
diff --git a/docs/reference/systems/physical/si_fps.rst b/docs/reference/systems/isq/si_fps.rst
similarity index 100%
rename from docs/reference/systems/physical/si_fps.rst
rename to docs/reference/systems/isq/si_fps.rst
diff --git a/docs/reference/systems/physical/si_iau.rst b/docs/reference/systems/isq/si_iau.rst
similarity index 100%
rename from docs/reference/systems/physical/si_iau.rst
rename to docs/reference/systems/isq/si_iau.rst
diff --git a/docs/reference/systems/physical/si_imperial.rst b/docs/reference/systems/isq/si_imperial.rst
similarity index 100%
rename from docs/reference/systems/physical/si_imperial.rst
rename to docs/reference/systems/isq/si_imperial.rst
diff --git a/docs/reference/systems/physical/si_international.rst b/docs/reference/systems/isq/si_international.rst
similarity index 100%
rename from docs/reference/systems/physical/si_international.rst
rename to docs/reference/systems/isq/si_international.rst
diff --git a/docs/reference/systems/physical/si_typographic.rst b/docs/reference/systems/isq/si_typographic.rst
similarity index 100%
rename from docs/reference/systems/physical/si_typographic.rst
rename to docs/reference/systems/isq/si_typographic.rst
diff --git a/docs/reference/systems/physical/si_us.rst b/docs/reference/systems/isq/si_us.rst
similarity index 100%
rename from docs/reference/systems/physical/si_us.rst
rename to docs/reference/systems/isq/si_us.rst
diff --git a/docs/use_cases.rst b/docs/use_cases.rst
index 29bcb2d9..6c84ef70 100644
--- a/docs/use_cases.rst
+++ b/docs/use_cases.rst
@@ -6,7 +6,7 @@ Use Cases
     For brevity all the code examples in this chapter assume::
 
         using namespace units;
-        using namespace units::physical;
+        using namespace units::isq;
 
 .. toctree::
     :maxdepth: 1
diff --git a/docs/use_cases/extensions.rst b/docs/use_cases/extensions.rst
index 83693c8d..97752d64 100644
--- a/docs/use_cases/extensions.rst
+++ b/docs/use_cases/extensions.rst
@@ -57,7 +57,7 @@ Enabling a Unit for Prefixing
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 In case I decide it is reasonable to express my desks with SI prefixes the only thing I have
-to change in the above code is to replace `no_prefix` with `physical::si::prefix`::
+to change in the above code is to replace `no_prefix` with `isq::si::prefix`::
 
     struct desk : named_scaled_unit<desk, "desk", si::prefix, ratio(3, 10), si::square_metre> {};
 
@@ -231,8 +231,8 @@ different systems:
 
     namespace si {
 
-    struct metre : named_unit<metre, "m", units::physical::si::prefix> {};
-    struct kilometre : prefixed_unit<kilometre, units::physical::si::kilo, metre> {};
+    struct metre : named_unit<metre, "m", units::isq::si::prefix> {};
+    struct kilometre : prefixed_unit<kilometre, units::isq::si::kilo, metre> {};
 
     struct dim_length : base_dimension<"L", metre> {};
 
diff --git a/docs/use_cases/interoperability.rst b/docs/use_cases/interoperability.rst
index f5e31a3c..764f3c14 100644
--- a/docs/use_cases/interoperability.rst
+++ b/docs/use_cases/interoperability.rst
@@ -16,14 +16,14 @@ provide the following:
 For example, to provide support for the ``std::chrono::duration`` it is enough to define::
 
     #include <units/customization_points.h>
-    #include <units/physical/si/time.h>
+    #include <units/isq/si/time.h>
     #include <chrono>
 
     namespace units {
 
     template<typename Rep, typename Period>
     struct quantity_like_traits<std::chrono::duration<Rep, Period>> {
-      using dimension = physical::si::dim_time;
+      using dimension = isq::si::dim_time;
       using unit = downcast_unit<dimension, ratio(Period::num, Period::den)>;
       using rep = Rep;
       [[nodiscard]] static constexpr rep count(const std::chrono::duration<Rep, Period>& q) { return q.count(); }
diff --git a/docs/use_cases/legacy_interfaces.rst b/docs/use_cases/legacy_interfaces.rst
index 4b6834b4..70e51b8c 100644
--- a/docs/use_cases/legacy_interfaces.rst
+++ b/docs/use_cases/legacy_interfaces.rst
@@ -25,10 +25,10 @@ and pass it to the library's output:
 .. code-block::
 
     #include "legacy.h"
-    #include <units/physical/si/si.h>
+    #include <units/isq/si/si.h>
     #include <units/quantity_point.h>
 
-    using namespace units::physical;
+    using namespace units::isq;
 
     constexpr Speed auto avg_speed(Length auto d, Time auto t)
     {
diff --git a/docs/use_cases/unknown_dimensions.rst b/docs/use_cases/unknown_dimensions.rst
index a79db984..705b34d5 100644
--- a/docs/use_cases/unknown_dimensions.rst
+++ b/docs/use_cases/unknown_dimensions.rst
@@ -22,9 +22,9 @@ The same applies to the resulting unit. For example:
 .. code-block::
     :emphasize-lines: 1,7,9
 
-    #include <units/physical/si/si.h>
+    #include <units/isq/si/si.h>
 
-    using namespace units::physical::si;
+    using namespace units::isq::si;
 
     constexpr auto result = 144_q_km / 2_q_h;
     static_assert(std::is_same_v<decltype(result)::dimension,
@@ -41,10 +41,10 @@ dimensions used in the division operation:
 .. code-block::
     :emphasize-lines: 1-2,8,10
 
-    #include <units/physical/si/length.h>
-    #include <units/physical/si/time.h>
+    #include <units/isq/si/length.h>
+    #include <units/isq/si/time.h>
 
-    using namespace units::physical::si;
+    using namespace units::isq::si;
 
     constexpr auto result = 144_q_km / 2_q_h;
     static_assert(std::is_same_v<decltype(result)::dimension,
@@ -55,7 +55,7 @@ dimensions used in the division operation:
 .. important::
 
     To limit the possibility of an ODR violation please always include a header file
-    with all the definitions for the current system (e.g. *units/physical/si/si.h*).
+    with all the definitions for the current system (e.g. *units/isq/si/si.h*).
 
 
 Operations On Unknown Dimensions And Their Units
diff --git a/example/alternative_namespaces/acceleration.h b/example/alternative_namespaces/acceleration.h
index 404a3187..4386d96e 100644
--- a/example/alternative_namespaces/acceleration.h
+++ b/example/alternative_namespaces/acceleration.h
@@ -1,7 +1,7 @@
 
 #pragma once
 
-#include <units/physical/si/acceleration.h>
+#include <units/isq/si/acceleration.h>
 
 namespace units{
 namespace experimental{
@@ -9,7 +9,7 @@ namespace experimental{
 namespace acceleration {
 
 template<typename Rep = double>
-using m_per_s2 = units::physical::si::acceleration<units::physical::si::metre_per_second_sq, Rep>;
+using m_per_s2 = units::isq::si::acceleration<units::isq::si::metre_per_second_sq, Rep>;
 
 template<typename Rep = double>
 constexpr m_per_s2<Rep> g{static_cast<Rep>(9.80665)};
diff --git a/example/alternative_namespaces/area.h b/example/alternative_namespaces/area.h
index fb1a9ab9..5a813674 100644
--- a/example/alternative_namespaces/area.h
+++ b/example/alternative_namespaces/area.h
@@ -1,14 +1,14 @@
 
 #pragma once
 
-#include <units/physical/si/area.h>
+#include <units/isq/si/area.h>
 
 namespace area {
 
 template<typename Rep = double>
-using m2 = units::physical::si::area<units::physical::si::square_metre, Rep>;
+using m2 = units::isq::si::area<units::isq::si::square_metre, Rep>;
 
 template<typename Rep = double>
-using fm2 = units::physical::si::area<units::physical::si::square_femtometre, Rep>;
+using fm2 = units::isq::si::area<units::isq::si::square_femtometre, Rep>;
 
 }  // namespace area
diff --git a/example/alternative_namespaces/box_example.cpp b/example/alternative_namespaces/box_example.cpp
index 18e597a9..06ae1aa1 100644
--- a/example/alternative_namespaces/box_example.cpp
+++ b/example/alternative_namespaces/box_example.cpp
@@ -53,7 +53,7 @@ struct Box {
 
 #include <iostream>
 
-using namespace units::physical::si::literals;
+using namespace units::isq::si::literals;
 
 int main()
 {
diff --git a/example/alternative_namespaces/capacitor_time_curve.cpp b/example/alternative_namespaces/capacitor_time_curve.cpp
index 1492db7e..e5a7285d 100644
--- a/example/alternative_namespaces/capacitor_time_curve.cpp
+++ b/example/alternative_namespaces/capacitor_time_curve.cpp
@@ -20,16 +20,16 @@
     physical_quantities
 */
 
-#include <units/physical/si/capacitance.h>
-#include <units/physical/si/resistance.h>
-#include <units/physical/si/time.h>
+#include <units/isq/si/capacitance.h>
+#include <units/isq/si/resistance.h>
+#include <units/isq/si/time.h>
 #include <units/math.h>
 #include <units/quantity_io.h>
 #include "./voltage.h"
 #include <iostream>
 
 using namespace units::experimental;
-using namespace units::physical::si::literals;
+using namespace units::isq::si::literals;
 
 int main()
 {
diff --git a/example/alternative_namespaces/clcpp_response.cpp b/example/alternative_namespaces/clcpp_response.cpp
index ac2336ba..06f77d7c 100644
--- a/example/alternative_namespaces/clcpp_response.cpp
+++ b/example/alternative_namespaces/clcpp_response.cpp
@@ -25,8 +25,8 @@
 #include "./area.h"
 #include "./units_str.h"
 
-using namespace units::physical::si::literals;
-using namespace units::physical::si::international;
+using namespace units::isq::si::literals;
+using namespace units::isq::si::international;
 using namespace units::experimental;
 
 void simple_quantities()
diff --git a/example/alternative_namespaces/conversion_factor.cpp b/example/alternative_namespaces/conversion_factor.cpp
index 685f45b4..c08eb4a2 100644
--- a/example/alternative_namespaces/conversion_factor.cpp
+++ b/example/alternative_namespaces/conversion_factor.cpp
@@ -41,7 +41,7 @@ inline constexpr std::common_type_t<typename Target::rep, typename Source::rep>
 
 }  // namespace
 
-using namespace units::physical::si::literals;
+using namespace units::isq::si::literals;
 using namespace units::experimental;
 
 int main()
diff --git a/example/alternative_namespaces/density.h b/example/alternative_namespaces/density.h
index 870da078..12a9dc78 100644
--- a/example/alternative_namespaces/density.h
+++ b/example/alternative_namespaces/density.h
@@ -2,7 +2,7 @@
 
 #pragma once
 
-#include <units/physical/si/density.h>
+#include <units/isq/si/density.h>
 
 namespace units{
 namespace experimental{
@@ -10,7 +10,7 @@ namespace experimental{
 namespace density {
 
 template<typename Rep = double>
-using kg_per_m3 = units::physical::si::density<units::physical::si::kilogram_per_metre_cub, Rep>;
+using kg_per_m3 = units::isq::si::density<units::isq::si::kilogram_per_metre_cub, Rep>;
 
 }
 
diff --git a/example/alternative_namespaces/force.h b/example/alternative_namespaces/force.h
index ad0945e5..346035d7 100644
--- a/example/alternative_namespaces/force.h
+++ b/example/alternative_namespaces/force.h
@@ -1,7 +1,7 @@
 
 #pragma once
 
-#include <units/physical/si/force.h>
+#include <units/isq/si/force.h>
 
 namespace units{
 namespace experimental{
@@ -9,7 +9,7 @@ namespace experimental{
 namespace force {
 
 template<typename Rep = double>
-using N = units::physical::si::force<units::physical::si::newton, Rep>;
+using N = units::isq::si::force<units::isq::si::newton, Rep>;
 
 }
 
diff --git a/example/alternative_namespaces/length.h b/example/alternative_namespaces/length.h
index d9a40687..9d96dd60 100644
--- a/example/alternative_namespaces/length.h
+++ b/example/alternative_namespaces/length.h
@@ -2,12 +2,12 @@
 
 #pragma once
 
-#include <units/physical/si/length.h>
-#include <units/physical/si/imperial/length.h>
-#include <units/physical/si/international/length.h>
-#include <units/physical/si/typographic/length.h>
-#include <units/physical/si/us/length.h>
-#include <units/physical/si/iau/length.h>
+#include <units/isq/si/length.h>
+#include <units/isq/si/imperial/length.h>
+#include <units/isq/si/international/length.h>
+#include <units/isq/si/typographic/length.h>
+#include <units/isq/si/us/length.h>
+#include <units/isq/si/iau/length.h>
 
 namespace units{
 namespace experimental{
@@ -15,70 +15,70 @@ namespace experimental{
 namespace length {
 
 template<typename Rep = double>
-using m = units::physical::si::length<units::physical::si::metre, Rep>;
+using m = units::isq::si::length<units::isq::si::metre, Rep>;
 
 template<typename Rep = double>
-using mm = units::physical::si::length<units::physical::si::millimetre, Rep>;
+using mm = units::isq::si::length<units::isq::si::millimetre, Rep>;
 
 template<typename Rep = double>
-using fm = units::physical::si::length<units::physical::si::femtometre, Rep>;
+using fm = units::isq::si::length<units::isq::si::femtometre, Rep>;
 
 template<typename Rep = double>
-using km = units::physical::si::length<units::physical::si::kilometre, Rep>;
+using km = units::isq::si::length<units::isq::si::kilometre, Rep>;
 
 template<typename Rep = double>
-using AU = units::physical::si::length<units::physical::si::astronomical_unit, Rep>;
+using AU = units::isq::si::length<units::isq::si::astronomical_unit, Rep>;
 
 template<typename Rep = double>
-using in = units::physical::si::length<units::physical::si::international::inch, Rep>;
+using in = units::isq::si::length<units::isq::si::international::inch, Rep>;
 
 template<typename Rep = double>
-using angstrom = units::physical::si::length<units::physical::si::iau::angstrom, Rep>;
+using angstrom = units::isq::si::length<units::isq::si::iau::angstrom, Rep>;
 
 template<typename Rep = double>
-using ch = units::physical::si::length<units::physical::si::imperial::chain, Rep>;
+using ch = units::isq::si::length<units::isq::si::imperial::chain, Rep>;
 
 template<typename Rep = double>
-using fathom = units::physical::si::length<units::physical::si::international::fathom, Rep>;
+using fathom = units::isq::si::length<units::isq::si::international::fathom, Rep>;
 
 template<typename Rep = double>
-using fathom_us = units::physical::si::length<units::physical::si::us::fathom, Rep>;
+using fathom_us = units::isq::si::length<units::isq::si::us::fathom, Rep>;
 
 template<typename Rep = double>
-using ft = units::physical::si::length<units::physical::si::international::foot, Rep>;
+using ft = units::isq::si::length<units::isq::si::international::foot, Rep>;
 
 template<typename Rep = double>
-using ft_us = units::physical::si::length<units::physical::si::us::foot, Rep>;
+using ft_us = units::isq::si::length<units::isq::si::us::foot, Rep>;
 
 template<typename Rep = double>
-using ly = units::physical::si::length<units::physical::si::iau::light_year, Rep>;
+using ly = units::isq::si::length<units::isq::si::iau::light_year, Rep>;
 
 template<typename Rep = double>
-using mi = units::physical::si::length<units::physical::si::international::mile, Rep>;
+using mi = units::isq::si::length<units::isq::si::international::mile, Rep>;
 
 template<typename Rep = double>
-using mi_naut = units::physical::si::length<units::physical::si::international::nautical_mile, Rep>;
+using mi_naut = units::isq::si::length<units::isq::si::international::nautical_mile, Rep>;
 
 template<typename Rep = double>
-using pc = units::physical::si::length<units::physical::si::iau::parsec, Rep>;
+using pc = units::isq::si::length<units::isq::si::iau::parsec, Rep>;
 
 template<typename Rep = double>
-using pica_comp = units::physical::si::length<units::physical::si::typographic::pica_comp, Rep>;
+using pica_comp = units::isq::si::length<units::isq::si::typographic::pica_comp, Rep>;
 
 template<typename Rep = double>
-using pica_prn = units::physical::si::length<units::physical::si::typographic::pica_prn, Rep>;
+using pica_prn = units::isq::si::length<units::isq::si::typographic::pica_prn, Rep>;
 
 template<typename Rep = double>
-using point_comp = units::physical::si::length<units::physical::si::typographic::point_comp, Rep>;
+using point_comp = units::isq::si::length<units::isq::si::typographic::point_comp, Rep>;
 
 template<typename Rep = double>
-using point_prn = units::physical::si::length<units::physical::si::typographic::point_prn, Rep>;
+using point_prn = units::isq::si::length<units::isq::si::typographic::point_prn, Rep>;
 
 template<typename Rep = double>
-using rd = units::physical::si::length<units::physical::si::imperial::rod, Rep>;
+using rd = units::isq::si::length<units::isq::si::imperial::rod, Rep>;
 
 template<typename Rep = double>
-using yd = units::physical::si::length<units::physical::si::international::yard, Rep>;
+using yd = units::isq::si::length<units::isq::si::international::yard, Rep>;
 
 
 }  // namespace length
diff --git a/example/alternative_namespaces/mass.h b/example/alternative_namespaces/mass.h
index 57816bc7..e8f4e60e 100644
--- a/example/alternative_namespaces/mass.h
+++ b/example/alternative_namespaces/mass.h
@@ -2,7 +2,7 @@
 
 #pragma once
 
-#include <units/physical/si/mass.h>
+#include <units/isq/si/mass.h>
 
 namespace units{
 namespace experimental{
@@ -10,7 +10,7 @@ namespace experimental{
 namespace mass {
 
 template<typename Rep = double>
-using kg = units::physical::si::mass<units::physical::si::kilogram, Rep>;
+using kg = units::isq::si::mass<units::isq::si::kilogram, Rep>;
 
 }
 
diff --git a/example/alternative_namespaces/time.h b/example/alternative_namespaces/time.h
index f1d6650f..cd9cfa2d 100644
--- a/example/alternative_namespaces/time.h
+++ b/example/alternative_namespaces/time.h
@@ -1,21 +1,21 @@
 
 #pragma once
 
-#include <units/physical/si/time.h>
+#include <units/isq/si/time.h>
 
 // named qtime due to conflict with time_t time(time_t*)
 namespace q_time {
 
 template<typename Rep = double>
-using s = units::physical::si::time<units::physical::si::second, Rep>;
+using s = units::isq::si::time<units::isq::si::second, Rep>;
 
 template<typename Rep = double>
-using ms = units::physical::si::time<units::physical::si::millisecond, Rep>;
+using ms = units::isq::si::time<units::isq::si::millisecond, Rep>;
 
 template<typename Rep = double>
-using min = units::physical::si::time<units::physical::si::minute, Rep>;
+using min = units::isq::si::time<units::isq::si::minute, Rep>;
 
 template<typename Rep = double>
-using h = units::physical::si::time<units::physical::si::hour, Rep>;
+using h = units::isq::si::time<units::isq::si::hour, Rep>;
 
 }  // namespace time
diff --git a/example/alternative_namespaces/timer.cpp b/example/alternative_namespaces/timer.cpp
index 50bd4984..c99848bd 100644
--- a/example/alternative_namespaces/timer.cpp
+++ b/example/alternative_namespaces/timer.cpp
@@ -8,7 +8,7 @@
 */
 
 using namespace units::experimental;
-using namespace units::physical::si::literals;
+using namespace units::isq::si::literals;
 
 int main()
 {
diff --git a/example/alternative_namespaces/units_str.h b/example/alternative_namespaces/units_str.h
index ba68a736..44e9883f 100644
--- a/example/alternative_namespaces/units_str.h
+++ b/example/alternative_namespaces/units_str.h
@@ -1,6 +1,6 @@
 #pragma once
 
-#include <units/physical/si/prefixes.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 // get at the units text of the quantity, without its numeric value
 inline auto constexpr units_str(const units::Quantity auto& q)
diff --git a/example/alternative_namespaces/voltage.h b/example/alternative_namespaces/voltage.h
index 258f597c..3e772e6e 100644
--- a/example/alternative_namespaces/voltage.h
+++ b/example/alternative_namespaces/voltage.h
@@ -2,7 +2,7 @@
 
 #pragma once
 
-#include <units/physical/si/voltage.h>
+#include <units/isq/si/voltage.h>
 
 namespace units{
 namespace experimental{
@@ -10,19 +10,19 @@ namespace experimental{
 namespace voltage {
 
 template<typename Rep = double>
-using V = units::physical::si::voltage<units::physical::si::volt, Rep>;
+using V = units::isq::si::voltage<units::isq::si::volt, Rep>;
 
 template<typename Rep = double>
-using mV = units::physical::si::voltage<units::physical::si::millivolt, Rep>;
+using mV = units::isq::si::voltage<units::isq::si::millivolt, Rep>;
 
 template<typename Rep = double>
-using uV = units::physical::si::voltage<units::physical::si::microvolt, Rep>;
+using uV = units::isq::si::voltage<units::isq::si::microvolt, Rep>;
 
 template<typename Rep = double>
-using nV = units::physical::si::voltage<units::physical::si::nanovolt, Rep>;
+using nV = units::isq::si::voltage<units::isq::si::nanovolt, Rep>;
 
 template<typename Rep = double>
-using pV = units::physical::si::voltage<units::physical::si::picovolt, Rep>;
+using pV = units::isq::si::voltage<units::isq::si::picovolt, Rep>;
 
 }  // namespace voltage
 
diff --git a/example/alternative_namespaces/volume.h b/example/alternative_namespaces/volume.h
index 9a201e49..0729eee0 100644
--- a/example/alternative_namespaces/volume.h
+++ b/example/alternative_namespaces/volume.h
@@ -2,7 +2,7 @@
 
 #pragma once
 
-#include <units/physical/si/volume.h>
+#include <units/isq/si/volume.h>
 
 namespace units{
 namespace experimental{
@@ -10,7 +10,7 @@ namespace experimental{
 namespace volume {
 
 template<typename Rep = double>
-using m3 = units::physical::si::volume<units::physical::si::cubic_metre, Rep>;
+using m3 = units::isq::si::volume<units::isq::si::cubic_metre, Rep>;
 
 }
 
diff --git a/example/avg_speed.cpp b/example/avg_speed.cpp
index 1ae667d9..e760d8ea 100644
--- a/example/avg_speed.cpp
+++ b/example/avg_speed.cpp
@@ -20,15 +20,15 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include <units/physical/si/cgs/speed.h>
-#include <units/physical/si/international/speed.h>
-#include <units/physical/si/speed.h>
+#include <units/isq/si/cgs/speed.h>
+#include <units/isq/si/international/speed.h>
+#include <units/isq/si/speed.h>
 #include <units/quantity_io.h>
 #include <iostream>
 
 namespace {
 
-using namespace units::physical;
+using namespace units::isq;
 
 constexpr si::speed<si::metre_per_second, int>
 fixed_int_si_avg_speed(si::length<si::metre, int> d,
@@ -68,7 +68,7 @@ void example()
 {
   // SI (int)
   {
-    using namespace units::physical::si::literals;
+    using namespace units::isq::si::literals;
     constexpr Length auto distance = 220_q_km;     // constructed from a UDL
     constexpr si::time<si::hour, int> duration(2); // constructed from a value
 
@@ -82,7 +82,7 @@ void example()
 
   // SI (double)
   {
-    using namespace units::physical::si::literals;
+    using namespace units::isq::si::literals;
     constexpr Length auto distance = 220._q_km; // constructed from a UDL
     constexpr si::time<si::hour> duration(2);   // constructed from a value
 
@@ -98,7 +98,7 @@ void example()
 
   // Customary Units (int)
   {
-    using namespace units::physical::si::international::literals;
+    using namespace units::isq::si::international::literals;
     constexpr Length auto distance = 140_q_mi;     // constructed from a UDL
     constexpr si::time<si::hour, int> duration(2); // constructed from a value
 
@@ -114,7 +114,7 @@ void example()
 
   // Customary Units (double)
   {
-    using namespace units::physical::si::international::literals;
+    using namespace units::isq::si::international::literals;
     constexpr Length auto distance = 140._q_mi; // constructed from a UDL
     constexpr si::time<si::hour> duration(2);   // constructed from a value
 
@@ -132,7 +132,7 @@ void example()
 
   // CGS (int)
   {
-    using namespace units::physical::si::cgs::literals;
+    using namespace units::isq::si::cgs::literals;
     constexpr Length auto distance = 22'000'000_q_cm; // constructed from a UDL
     constexpr si::cgs::time<si::hour, int> duration(2);   // constructed from a value
 
@@ -151,7 +151,7 @@ void example()
 
   // CGS (double)
   {
-    using namespace units::physical::si::cgs::literals;
+    using namespace units::isq::si::cgs::literals;
     constexpr Length auto distance = 22'000'000._q_cm; // constructed from a UDL
     constexpr si::cgs::time<si::hour> duration(2);     // constructed from a value
 
diff --git a/example/box_example.cpp b/example/box_example.cpp
index 5ed8de99..9ac3b645 100644
--- a/example/box_example.cpp
+++ b/example/box_example.cpp
@@ -1,18 +1,18 @@
-#include <units/physical/si/constants.h>
-#include <units/physical/si/area.h>
-#include <units/physical/si/speed.h>
-#include <units/physical/si/density.h>
-#include <units/physical/si/force.h>
-#include <units/physical/si/mass.h>
-#include <units/physical/si/time.h>
-#include <units/physical/si/volume.h>
+#include <units/isq/si/constants.h>
+#include <units/isq/si/area.h>
+#include <units/isq/si/speed.h>
+#include <units/isq/si/density.h>
+#include <units/isq/si/force.h>
+#include <units/isq/si/mass.h>
+#include <units/isq/si/time.h>
+#include <units/isq/si/volume.h>
 #include <units/format.h>
 #include <cassert>
 #include <iostream>
 
 namespace {
 
-using namespace units::physical;
+using namespace units::isq;
 
 using m = si::metre;
 using m2 = si::square_metre;
diff --git a/example/capacitor_time_curve.cpp b/example/capacitor_time_curve.cpp
index bc6ee838..af75e6d2 100644
--- a/example/capacitor_time_curve.cpp
+++ b/example/capacitor_time_curve.cpp
@@ -20,18 +20,18 @@
     physical_quantities
 */
 
-#include <units/physical/si/capacitance.h>
-#include <units/physical/si/resistance.h>
-#include <units/physical/si/time.h>
-#include <units/physical/si/voltage.h>
+#include <units/isq/si/capacitance.h>
+#include <units/isq/si/resistance.h>
+#include <units/isq/si/time.h>
+#include <units/isq/si/voltage.h>
 #include <units/math.h>
 #include <units/quantity_io.h>
 #include <iostream>
 
 int main()
 {
-  using namespace units::physical;
-  using namespace units::physical::si;
+  using namespace units::isq;
+  using namespace units::isq::si;
 
   std::cout << "mp-units capacitor time curve example...\n";
   std::cout.setf(std::ios_base::fixed, std::ios_base::floatfield);
diff --git a/example/clcpp_response.cpp b/example/clcpp_response.cpp
index 83827f66..a098d920 100644
--- a/example/clcpp_response.cpp
+++ b/example/clcpp_response.cpp
@@ -16,15 +16,15 @@
 */
 
 #include <units/format.h>
-#include <units/physical/si/area.h>
-#include <units/physical/si/iau/length.h>
-#include <units/physical/si/imperial/length.h>
-#include <units/physical/si/international/length.h>
-#include <units/physical/si/length.h>
-#include <units/physical/si/time.h>
-#include <units/physical/si/typographic/length.h>
-#include <units/physical/si/us/length.h>
-#include <units/physical/si/volume.h>
+#include <units/isq/si/area.h>
+#include <units/isq/si/iau/length.h>
+#include <units/isq/si/imperial/length.h>
+#include <units/isq/si/international/length.h>
+#include <units/isq/si/length.h>
+#include <units/isq/si/time.h>
+#include <units/isq/si/typographic/length.h>
+#include <units/isq/si/us/length.h>
+#include <units/isq/si/volume.h>
 #include <units/quantity_io.h>
 #include <iostream>
 
@@ -34,11 +34,11 @@ using namespace units;
 
 void simple_quantities()
 {
-  using namespace units::physical::si;
-  using namespace units::physical::si::international;
+  using namespace units::isq::si;
+  using namespace units::isq::si::international;
 
   using distance = length<metre>;
-  using duration = physical::si::time<second>;
+  using duration = isq::si::time<second>;
 
   constexpr distance km = 1.0_q_km;
   constexpr distance miles = 1.0_q_mi;
@@ -58,9 +58,9 @@ void simple_quantities()
 
 void quantities_with_typed_units()
 {
-  using namespace units::physical;
-  using namespace units::physical::si;
-  using namespace units::physical::si::international;
+  using namespace units::isq;
+  using namespace units::isq::si;
+  using namespace units::isq::si::international;
 
   constexpr length<kilometre> km = 1.0_q_km;
   constexpr length<mile> miles = 1.0_q_mi;
@@ -106,7 +106,7 @@ void quantities_with_typed_units()
 
 void calcs_comparison()
 {
-  using namespace units::physical::si;
+  using namespace units::isq::si;
 
   std::cout << "\nA distinct unit for each type is efficient and accurate\n"
                "when adding two values of the same very big\n"
diff --git a/example/conversion_factor.cpp b/example/conversion_factor.cpp
index ffe2abb1..c2d1bb00 100644
--- a/example/conversion_factor.cpp
+++ b/example/conversion_factor.cpp
@@ -15,7 +15,7 @@
  along with this program. If not, see http://www.gnu.org/licenses./
 */
 
-#include <units/physical/si/length.h>
+#include <units/isq/si/length.h>
 #include <units/format.h>
 #include <units/quantity_io.h>
 #include <iostream>
@@ -42,7 +42,7 @@ inline constexpr std::common_type_t<typename Target::rep, typename Source::rep>
 
 int main()
 {
-  using namespace units::physical::si;
+  using namespace units::isq::si;
 
   std::cout << "conversion factor in mp-units...\n\n";
 
diff --git a/example/custom_systems.cpp b/example/custom_systems.cpp
index ea2c47ba..82f911c2 100644
--- a/example/custom_systems.cpp
+++ b/example/custom_systems.cpp
@@ -21,7 +21,7 @@
 // SOFTWARE.
 
 #include <units/quantity_io.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/si/prefixes.h>
 #include <iostream>
 
 using namespace units;
@@ -40,8 +40,8 @@ using length = quantity<dim_length, U, Rep>;
 
 namespace si {
 
-struct metre : named_unit<metre, "m", units::physical::si::prefix> {};
-struct kilometre : prefixed_unit<kilometre, units::physical::si::kilo, metre> {};
+struct metre : named_unit<metre, "m", units::isq::si::prefix> {};
+struct kilometre : prefixed_unit<kilometre, units::isq::si::kilo, metre> {};
 
 struct dim_length : base_dimension<"L", metre> {};
 
diff --git a/example/experimental_angle.cpp b/example/experimental_angle.cpp
index 116660e4..4080bf81 100644
--- a/example/experimental_angle.cpp
+++ b/example/experimental_angle.cpp
@@ -22,14 +22,14 @@
 
 #include <units/format.h>
 #include <units/generic/angle.h>
-#include <units/physical/si/length.h>
-#include <units/physical/si/energy.h>
-#include <units/physical/si/torque.h>
+#include <units/isq/si/length.h>
+#include <units/isq/si/energy.h>
+#include <units/isq/si/torque.h>
 #include <units/quantity_io.h>
 #include <iostream>
 
 using namespace units;
-using namespace units::physical::si::literals;
+using namespace units::isq::si::literals;
 
 int main()
 {
diff --git a/example/foot_pound_second.cpp b/example/foot_pound_second.cpp
index 81d64649..ea54a1ae 100644
--- a/example/foot_pound_second.cpp
+++ b/example/foot_pound_second.cpp
@@ -22,21 +22,21 @@
 
 #include <units/concepts.h>
 #include <units/format.h>
-#include <units/physical/si/fps/density.h>
-#include <units/physical/si/fps/length.h>
-#include <units/physical/si/fps/mass.h>
-#include <units/physical/si/fps/power.h>
-#include <units/physical/si/fps/speed.h>
-#include <units/physical/si/fps/volume.h>
-#include <units/physical/si/length.h>
-#include <units/physical/si/mass.h>
-#include <units/physical/si/power.h>
-#include <units/physical/si/speed.h>
-#include <units/physical/si/volume.h>
+#include <units/isq/si/fps/density.h>
+#include <units/isq/si/fps/length.h>
+#include <units/isq/si/fps/mass.h>
+#include <units/isq/si/fps/power.h>
+#include <units/isq/si/fps/speed.h>
+#include <units/isq/si/fps/volume.h>
+#include <units/isq/si/length.h>
+#include <units/isq/si/mass.h>
+#include <units/isq/si/power.h>
+#include <units/isq/si/speed.h>
+#include <units/isq/si/volume.h>
 #include <units/quantity.h>
 #include <iostream>
 
-using namespace units::physical;
+using namespace units::isq;
 
 
 // Some basic specs for the warship   
@@ -64,7 +64,7 @@ auto fmt_line(const Q a)
 // Print the ship details in the units as defined in the Ship struct, in other si::imperial units, and in SI
 void print_details(std::string_view description, const Ship& ship)
 {
-  using namespace units::physical::si::fps::literals;
+  using namespace units::isq::si::fps::literals;
   const auto waterDensity = 62.4_q_lb_per_ft3;
   std::cout << fmt::format("{}\n", description);
   std::cout << fmt::format("{:20} : {}\n", "length",    fmt_line<si::fps::length<si::fps::yard>, si::length<si::metre>>(ship.length))
@@ -81,8 +81,8 @@ void print_details(std::string_view description, const Ship& ship)
 
 int main()
 {
-  using namespace units::physical::si::literals;
-  using namespace units::physical::si::fps::literals;
+  using namespace units::isq::si::literals;
+  using namespace units::isq::si::fps::literals;
   
   // KMS Bismark, using the units the Germans would use, taken from Wiki
   auto bismark = Ship{.length{251._q_m}, .draft{9.3_q_m}, .beam{36_q_m}, .speed{56_q_km_per_h}, .mass{50'300_q_t}, .mainGuns{380_q_mm}, .shellMass{800_q_kg}, .shellSpeed{820._q_m_per_s}, .power{110.45_q_kW}};
diff --git a/example/geographic.cpp b/example/geographic.cpp
index 214775d7..a287d3f3 100644
--- a/example/geographic.cpp
+++ b/example/geographic.cpp
@@ -26,7 +26,7 @@
 
 namespace {
 
-using namespace units::physical::si::unit_constants;
+using namespace units::isq::si::unit_constants;
 inline constexpr auto earth_radius = 6371 * km;
 
 }  // namespace
diff --git a/example/geographic.h b/example/geographic.h
index ed0c9edb..6bd33522 100644
--- a/example/geographic.h
+++ b/example/geographic.h
@@ -23,7 +23,7 @@
 #pragma once
 
 #include <units/format.h>
-#include <units/physical/si/length.h>
+#include <units/isq/si/length.h>
 #include <units/quantity_kind.h>
 #include <compare>
 
@@ -116,8 +116,8 @@ struct fmt::formatter<geographic::longitude> : formatter<geographic::longitude::
 
 namespace geographic {
 
-struct horizontal_kind : units::kind<horizontal_kind, units::physical::si::dim_length> {};
-using distance = units::quantity_kind<horizontal_kind, units::physical::si::kilometre>;
+struct horizontal_kind : units::kind<horizontal_kind, units::isq::si::dim_length> {};
+using distance = units::quantity_kind<horizontal_kind, units::isq::si::kilometre>;
 
 struct position {
   latitude lat;
diff --git a/example/glide_computer.h b/example/glide_computer.h
index cedbb893..f1b94008 100644
--- a/example/glide_computer.h
+++ b/example/glide_computer.h
@@ -25,8 +25,8 @@
 #include "geographic.h"
 #include <units/format.h>
 #include <units/math.h>
-#include <units/physical/si/speed.h>
-#include <units/physical/si/international/length.h>
+#include <units/isq/si/speed.h>
+#include <units/isq/si/international/length.h>
 #include <units/quantity_point_kind.h>
 
 // An example of a really simplified tactical glide computer
@@ -44,7 +44,7 @@
 // - flight path exactly on a shortest possible line to destination
 
 using namespace units;
-using namespace units::physical;
+using namespace units::isq;
 
 template<units::QuantityKind QK>
 struct fmt::formatter<QK> : formatter<typename QK::quantity_type> {
@@ -95,11 +95,11 @@ std::basic_ostream<CharT, Traits>& operator<<(std::basic_ostream<CharT, Traits>&
 }  // namespace glide_computer
 
 template<>
-struct fmt::formatter<glide_computer::altitude> : formatter<units::physical::si::length<units::physical::si::metre>> {
+struct fmt::formatter<glide_computer::altitude> : formatter<units::isq::si::length<units::isq::si::metre>> {
   template<typename FormatContext>
   auto format(glide_computer::altitude a, FormatContext& ctx)
   {
-    formatter<units::physical::si::length<units::physical::si::metre>>::format(a.relative().common(), ctx);
+    formatter<units::isq::si::length<units::isq::si::metre>>::format(a.relative().common(), ctx);
     return format_to(ctx.out(), " AMSL");
   }
 };
diff --git a/example/glide_computer_example.cpp b/example/glide_computer_example.cpp
index b770c58c..e48951ce 100644
--- a/example/glide_computer_example.cpp
+++ b/example/glide_computer_example.cpp
@@ -53,7 +53,7 @@ auto get_weather_conditions()
 auto get_waypoints()
 {
   using namespace geographic::literals;
-  using namespace units::physical::si::international::unit_constants;
+  using namespace units::isq::si::international::unit_constants;
   static const std::array waypoints = {
       waypoint{"EPPR", {54.24772_N, 18.6745_E}, altitude(16 * ft)},    // N54°14'51.8" E18°40'28.2"
       waypoint{"EPGI", {53.52442_N, 18.84947_E}, altitude(115 * ft)}   // N53°31'27.9" E18°50'58.1"
diff --git a/example/hello_units.cpp b/example/hello_units.cpp
index 60a3099f..3d45255e 100644
--- a/example/hello_units.cpp
+++ b/example/hello_units.cpp
@@ -21,12 +21,12 @@
 // SOFTWARE.
 
 #include <units/format.h>
-#include <units/physical/si/international/speed.h>
-#include <units/physical/si/speed.h>
+#include <units/isq/si/international/speed.h>
+#include <units/isq/si/speed.h>
 #include <units/quantity_io.h>
 #include <iostream>
 
-using namespace units::physical;
+using namespace units::isq;
 
 constexpr Speed auto avg_speed(Length auto d, Time auto t)
 {
@@ -35,8 +35,8 @@ constexpr Speed auto avg_speed(Length auto d, Time auto t)
 
 int main()
 {
-  using namespace units::physical::si::literals;
-  using namespace units::physical::si::unit_constants;
+  using namespace units::isq::si::literals;
+  using namespace units::isq::si::unit_constants;
 
   constexpr Speed auto v1 = 110 * km / h;
   constexpr Speed auto v2 = avg_speed(220_q_km, 2_q_h);
diff --git a/example/kalman_filter-alpha_beta_filter_example2.cpp b/example/kalman_filter-alpha_beta_filter_example2.cpp
index c0e47acc..f970d2d9 100644
--- a/example/kalman_filter-alpha_beta_filter_example2.cpp
+++ b/example/kalman_filter-alpha_beta_filter_example2.cpp
@@ -1,5 +1,5 @@
 #include <units/format.h>
-#include <units/physical/si/speed.h>
+#include <units/isq/si/speed.h>
 #include <iostream>
 #include <array>
 
@@ -16,8 +16,8 @@ struct state_variable {
   Q predicted_next_state;
 };
 
-using namespace units::physical;
-using namespace units::physical::si::literals;
+using namespace units::isq;
+using namespace units::isq::si::literals;
 
 constexpr auto radar_transmit_interval = 5.0_q_s;
 constexpr double kalman_range_gain = 0.2;
diff --git a/example/linear_algebra.cpp b/example/linear_algebra.cpp
index ee993df9..463bfe4b 100644
--- a/example/linear_algebra.cpp
+++ b/example/linear_algebra.cpp
@@ -20,9 +20,9 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include <units/physical/si/speed.h>
-#include <units/physical/si/force.h>
-#include <units/physical/si/energy.h>
+#include <units/isq/si/speed.h>
+#include <units/isq/si/force.h>
+#include <units/isq/si/energy.h>
 #include <units/format.h>
 #include <units/quantity_io.h>
 #include <linear_algebra.hpp>
@@ -58,8 +58,8 @@ std::ostream& operator<<(std::ostream& os, const matrix<ET, OT>& v)
 
 namespace {
 
-using namespace units::physical;
-using namespace units::physical::si::literals;
+using namespace units::isq;
+using namespace units::isq::si::literals;
 
 template<typename Rep = double>
 using vector = std::math::fs_vector<Rep, 3>;
diff --git a/example/measurement.cpp b/example/measurement.cpp
index 819277c1..da1c8e38 100644
--- a/example/measurement.cpp
+++ b/example/measurement.cpp
@@ -20,7 +20,7 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include <units/physical/si/acceleration.h>
+#include <units/isq/si/acceleration.h>
 #include <units/quantity_io.h>
 #include <cmath>
 #include <compare>
@@ -124,7 +124,7 @@ static_assert(units::QuantityValue<measurement<double>>);
 
 void example()
 {
-  using namespace units::physical;
+  using namespace units::isq;
 
   const auto a = si::acceleration<si::metre_per_second_sq, measurement<double>>(measurement(9.8, 0.1));
   const auto t = si::time<si::second, measurement<double>>(measurement(1.2, 0.1));
diff --git a/example/total_energy.cpp b/example/total_energy.cpp
index d4d7e50c..543b394a 100644
--- a/example/total_energy.cpp
+++ b/example/total_energy.cpp
@@ -20,18 +20,18 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include <units/physical/natural/constants.h>
-#include <units/physical/si/energy.h>
-#include <units/physical/si/momentum.h>
-#include <units/physical/si/speed.h>
-#include <units/physical/si/constants.h>
+#include <units/isq/natural/constants.h>
+#include <units/isq/si/energy.h>
+#include <units/isq/si/momentum.h>
+#include <units/isq/si/speed.h>
+#include <units/isq/si/constants.h>
 #include <units/math.h>
 #include <units/quantity_io.h>
 #include <iostream>
 
 namespace {
 
-using namespace units::physical;
+using namespace units::isq;
 
 Energy auto total_energy(Momentum auto p, Mass auto m, Speed auto c)
 {
@@ -40,7 +40,7 @@ Energy auto total_energy(Momentum auto p, Mass auto m, Speed auto c)
 
 void si_example()
 {
-  using namespace units::physical::si;
+  using namespace units::isq::si;
   using GeV = gigaelectronvolt;
 
   constexpr Speed auto c = si2019::speed_of_light<>;
@@ -71,7 +71,7 @@ void si_example()
 
 void natural_example()
 {
-  using namespace units::physical::natural;
+  using namespace units::isq::natural;
   using GeV = gigaelectronvolt;
 
   constexpr Speed auto c = speed_of_light<>;
diff --git a/example/unknown_dimension.cpp b/example/unknown_dimension.cpp
index 822a18e0..dea18b0b 100644
--- a/example/unknown_dimension.cpp
+++ b/example/unknown_dimension.cpp
@@ -20,22 +20,22 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include <units/physical/si/speed.h>
+#include <units/isq/si/speed.h>
 #include <units/quantity_io.h>
 #include <iostream>
 
 namespace {
 
-template<units::physical::Length D, units::physical::Time T>
-constexpr units::physical::Speed auto avg_speed(D d, T t)
+template<units::isq::Length D, units::isq::Time T>
+constexpr units::isq::Speed auto avg_speed(D d, T t)
 {
   return d / t;
 }
 
 void example()
 {
-  using namespace units::physical;
-  using namespace units::physical::si::literals;
+  using namespace units::isq;
+  using namespace units::isq::si::literals;
 
   Length auto d1 = 123_q_m;
   Time auto t1 = 10_q_s;
diff --git a/src/include/units/chrono.h b/src/include/units/chrono.h
index 9b6ff25b..b8400b99 100644
--- a/src/include/units/chrono.h
+++ b/src/include/units/chrono.h
@@ -23,14 +23,14 @@
 #pragma once
 
 #include <units/customization_points.h>
-#include <units/physical/si/time.h>
+#include <units/isq/si/time.h>
 #include <chrono>
 
 namespace units {
 
 template<typename Rep, typename Period>
 struct quantity_like_traits<std::chrono::duration<Rep, Period>> {
-  using dimension = physical::si::dim_time;
+  using dimension = isq::si::dim_time;
   using unit = downcast_unit<dimension, ratio(Period::num, Period::den)>;
   using rep = Rep;
   [[nodiscard]] static constexpr rep count(const std::chrono::duration<Rep, Period>& q) { return q.count(); }
@@ -38,7 +38,7 @@ struct quantity_like_traits<std::chrono::duration<Rep, Period>> {
 
 template<typename C, typename Rep, typename Period>
 struct quantity_point_like_traits<std::chrono::time_point<C, std::chrono::duration<Rep, Period>>> {
-  using dimension = physical::si::dim_time;
+  using dimension = isq::si::dim_time;
   using unit = downcast_unit<dimension, ratio(Period::num, Period::den)>;
   using rep = Rep;
   [[nodiscard]] static constexpr auto relative(
diff --git a/src/include/units/data/bitrate.h b/src/include/units/data/bitrate.h
index cb99ffd0..4ebd8cf8 100644
--- a/src/include/units/data/bitrate.h
+++ b/src/include/units/data/bitrate.h
@@ -24,19 +24,19 @@
 
 #include <units/data/information.h>
 #include <units/derived_dimension.h>
-#include <units/physical/si/time.h>
+#include <units/isq/si/time.h>
 #include <units/quantity.h>
 
 namespace units::data {
 
 struct bit_per_second : unit<bit_per_second> {};
-struct dim_bitrate : derived_dimension<dim_bitrate, bit_per_second, exponent<dim_information, 1>, exponent<physical::si::dim_time, -1>> {};
+struct dim_bitrate : derived_dimension<dim_bitrate, bit_per_second, exponent<dim_information, 1>, exponent<isq::si::dim_time, -1>> {};
 
-struct kibibit_per_second : deduced_unit<kibibit_per_second, dim_bitrate, kibibit, physical::si::second> {};
-struct mebibit_per_second : deduced_unit<mebibit_per_second, dim_bitrate, mebibit, physical::si::second> {};
-struct gibibit_per_second : deduced_unit<gibibit_per_second, dim_bitrate, gibibit, physical::si::second> {};
-struct tebibit_per_second : deduced_unit<tebibit_per_second, dim_bitrate, tebibit, physical::si::second> {};
-struct pebibit_per_second : deduced_unit<pebibit_per_second, dim_bitrate, pebibit, physical::si::second> {};
+struct kibibit_per_second : deduced_unit<kibibit_per_second, dim_bitrate, kibibit, isq::si::second> {};
+struct mebibit_per_second : deduced_unit<mebibit_per_second, dim_bitrate, mebibit, isq::si::second> {};
+struct gibibit_per_second : deduced_unit<gibibit_per_second, dim_bitrate, gibibit, isq::si::second> {};
+struct tebibit_per_second : deduced_unit<tebibit_per_second, dim_bitrate, tebibit, isq::si::second> {};
+struct pebibit_per_second : deduced_unit<pebibit_per_second, dim_bitrate, pebibit, isq::si::second> {};
 
 template<typename T>
 concept Bitrate = QuantityOf<T, dim_bitrate>;
diff --git a/src/include/units/generic/angle.h b/src/include/units/generic/angle.h
index f91f0118..f9a393b6 100644
--- a/src/include/units/generic/angle.h
+++ b/src/include/units/generic/angle.h
@@ -22,12 +22,12 @@
 
 #pragma once
 
-#include <units/physical/si/prefixes.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
 namespace units {
 
-struct radian : named_unit<radian, "rad", physical::si::prefix> {};
+struct radian : named_unit<radian, "rad", isq::si::prefix> {};
 
 template<Unit U = radian>
 struct dim_angle : base_dimension<"A", U> {};
diff --git a/src/include/units/isq/dimensions.h b/src/include/units/isq/dimensions.h
new file mode 100644
index 00000000..ec8d9473
--- /dev/null
+++ b/src/include/units/isq/dimensions.h
@@ -0,0 +1,70 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2018 Mateusz Pusz
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#pragma once
+
+#include <units/isq/dimensions/absorbed_dose.h>
+#include <units/isq/dimensions/acceleration.h>
+#include <units/isq/dimensions/amount_of_substance.h>
+#include <units/isq/dimensions/angular_velocity.h>
+#include <units/isq/dimensions/area.h>
+#include <units/isq/dimensions/capacitance.h>
+#include <units/isq/dimensions/catalytic_activity.h>
+#include <units/isq/dimensions/charge_density.h>
+#include <units/isq/dimensions/concentration.h>
+#include <units/isq/dimensions/conductance.h>
+#include <units/isq/dimensions/current_density.h>
+#include <units/isq/dimensions/density.h>
+#include <units/isq/dimensions/dynamic_viscosity.h>
+#include <units/isq/dimensions/electric_charge.h>
+#include <units/isq/dimensions/electric_current.h>
+#include <units/isq/dimensions/electric_field_strength.h>
+#include <units/isq/dimensions/energy.h>
+// TODO Add when downcasting issue is solved (collides with pressure)
+// #include <units/isq/dimensions/energy_density.h>
+#include <units/isq/dimensions/force.h>
+#include <units/isq/dimensions/frequency.h>
+#include <units/isq/dimensions/heat_capacity.h>
+#include <units/isq/dimensions/inductance.h>
+#include <units/isq/dimensions/length.h>
+#include <units/isq/dimensions/luminance.h>
+#include <units/isq/dimensions/luminous_intensity.h>
+#include <units/isq/dimensions/magnetic_flux.h>
+#include <units/isq/dimensions/magnetic_induction.h>
+#include <units/isq/dimensions/mass.h>
+#include <units/isq/dimensions/molar_energy.h>
+#include <units/isq/dimensions/momentum.h>
+#include <units/isq/dimensions/permeability.h>
+#include <units/isq/dimensions/permittivity.h>
+#include <units/isq/dimensions/power.h>
+#include <units/isq/dimensions/pressure.h>
+// TODO Add when downcasting issue is solved (collides with frequency)
+// #include <units/isq/dimensions/radioactivity.h>
+#include <units/isq/dimensions/resistance.h>
+#include <units/isq/dimensions/speed.h>
+#include <units/isq/dimensions/surface_tension.h>
+#include <units/isq/dimensions/thermal_conductivity.h>
+#include <units/isq/dimensions/thermodynamic_temperature.h>
+#include <units/isq/dimensions/time.h>
+#include <units/isq/dimensions/torque.h>
+#include <units/isq/dimensions/voltage.h>
+#include <units/isq/dimensions/volume.h>
diff --git a/src/include/units/physical/dimensions/absorbed_dose.h b/src/include/units/isq/dimensions/absorbed_dose.h
similarity index 90%
rename from src/include/units/physical/dimensions/absorbed_dose.h
rename to src/include/units/isq/dimensions/absorbed_dose.h
index 1e6e65e2..8dcb1e6c 100644
--- a/src/include/units/physical/dimensions/absorbed_dose.h
+++ b/src/include/units/isq/dimensions/absorbed_dose.h
@@ -23,10 +23,10 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/energy.h>
-#include <units/physical/dimensions/mass.h>
+#include <units/isq/dimensions/energy.h>
+#include <units/isq/dimensions/mass.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_energy> E, DimensionOfT<dim_mass> M>
 struct dim_absorbed_dose : derived_dimension<Child, U, exponent<E, 1>, exponent<M, -1>> {};
@@ -34,4 +34,4 @@ struct dim_absorbed_dose : derived_dimension<Child, U, exponent<E, 1>, exponent<
 template<typename T>
 concept AbsorbedDose = QuantityOfT<T, dim_absorbed_dose>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/acceleration.h b/src/include/units/isq/dimensions/acceleration.h
similarity index 90%
rename from src/include/units/physical/dimensions/acceleration.h
rename to src/include/units/isq/dimensions/acceleration.h
index 86b94505..b639fcca 100644
--- a/src/include/units/physical/dimensions/acceleration.h
+++ b/src/include/units/isq/dimensions/acceleration.h
@@ -23,10 +23,10 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/length.h>
-#include <units/physical/dimensions/time.h>
+#include <units/isq/dimensions/length.h>
+#include <units/isq/dimensions/time.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_length> L, DimensionOfT<dim_time> T>
 struct dim_acceleration : derived_dimension<Child, U, exponent<L, 1>, exponent<T, -2>> {};
@@ -34,4 +34,4 @@ struct dim_acceleration : derived_dimension<Child, U, exponent<L, 1>, exponent<T
 template<typename T>
 concept Acceleration = QuantityOfT<T, dim_acceleration>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/amount_of_substance.h b/src/include/units/isq/dimensions/amount_of_substance.h
similarity index 95%
rename from src/include/units/physical/dimensions/amount_of_substance.h
rename to src/include/units/isq/dimensions/amount_of_substance.h
index ffa42303..099e516f 100644
--- a/src/include/units/physical/dimensions/amount_of_substance.h
+++ b/src/include/units/isq/dimensions/amount_of_substance.h
@@ -24,7 +24,7 @@
 
 #include <units/concepts.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<Unit U>
 struct dim_amount_of_substance : base_dimension<"N", U> {};
@@ -32,4 +32,4 @@ struct dim_amount_of_substance : base_dimension<"N", U> {};
 template<typename T>
 concept AmountOfSubstance = QuantityOfT<T, dim_amount_of_substance>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/angular_velocity.h b/src/include/units/isq/dimensions/angular_velocity.h
similarity index 93%
rename from src/include/units/physical/dimensions/angular_velocity.h
rename to src/include/units/isq/dimensions/angular_velocity.h
index 1e50a165..dfea55d1 100644
--- a/src/include/units/physical/dimensions/angular_velocity.h
+++ b/src/include/units/isq/dimensions/angular_velocity.h
@@ -24,9 +24,9 @@
 
 #include <units/generic/angle.h>
 #include <units/concepts.h>
-#include <units/physical/dimensions/time.h>
+#include <units/isq/dimensions/time.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_angle> A, DimensionOfT<dim_time> T>
 struct dim_angular_velocity : derived_dimension<Child, U, exponent<A, 1>, exponent<T, -1>> {};
@@ -34,4 +34,4 @@ struct dim_angular_velocity : derived_dimension<Child, U, exponent<A, 1>, expone
 template <typename T>
 concept AngularVelocity = QuantityOfT<T, dim_angular_velocity>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/area.h b/src/include/units/isq/dimensions/area.h
similarity index 92%
rename from src/include/units/physical/dimensions/area.h
rename to src/include/units/isq/dimensions/area.h
index 4a6356dc..c122a00a 100644
--- a/src/include/units/physical/dimensions/area.h
+++ b/src/include/units/isq/dimensions/area.h
@@ -23,9 +23,9 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/length.h>
+#include <units/isq/dimensions/length.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_length> L>
 struct dim_area : derived_dimension<Child, U, exponent<L, 2>> {};
@@ -33,4 +33,4 @@ struct dim_area : derived_dimension<Child, U, exponent<L, 2>> {};
 template<typename T>
 concept Area = QuantityOfT<T, dim_area>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/capacitance.h b/src/include/units/isq/dimensions/capacitance.h
similarity index 89%
rename from src/include/units/physical/dimensions/capacitance.h
rename to src/include/units/isq/dimensions/capacitance.h
index acb96153..8a7f1c72 100644
--- a/src/include/units/physical/dimensions/capacitance.h
+++ b/src/include/units/isq/dimensions/capacitance.h
@@ -23,10 +23,10 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/electric_charge.h>
-#include <units/physical/dimensions/voltage.h>
+#include <units/isq/dimensions/electric_charge.h>
+#include <units/isq/dimensions/voltage.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_electric_charge> C, DimensionOfT<dim_voltage> V>
 struct dim_capacitance : derived_dimension<Child, U, exponent<C, 1>, exponent<V, -1>> {};
@@ -34,4 +34,4 @@ struct dim_capacitance : derived_dimension<Child, U, exponent<C, 1>, exponent<V,
 template<typename T>
 concept Capacitance = QuantityOfT<T, dim_capacitance>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/catalytic_activity.h b/src/include/units/isq/dimensions/catalytic_activity.h
similarity index 90%
rename from src/include/units/physical/dimensions/catalytic_activity.h
rename to src/include/units/isq/dimensions/catalytic_activity.h
index e7b0f19b..82b21dc1 100644
--- a/src/include/units/physical/dimensions/catalytic_activity.h
+++ b/src/include/units/isq/dimensions/catalytic_activity.h
@@ -22,11 +22,11 @@
 
 #pragma once
 
-#include <units/physical/dimensions/amount_of_substance.h>
+#include <units/isq/dimensions/amount_of_substance.h>
 #include <units/concepts.h>
-#include <units/physical/dimensions/time.h>
+#include <units/isq/dimensions/time.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_time> T, DimensionOfT<dim_amount_of_substance> M>
 struct dim_catalytic_activity : derived_dimension<Child, U, exponent<T, -1>, exponent<M, 1>> {};
@@ -34,4 +34,4 @@ struct dim_catalytic_activity : derived_dimension<Child, U, exponent<T, -1>, exp
 template<typename T>
 concept CatalyticActivity = QuantityOfT<T, dim_catalytic_activity>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/charge_density.h b/src/include/units/isq/dimensions/charge_density.h
similarity index 91%
rename from src/include/units/physical/dimensions/charge_density.h
rename to src/include/units/isq/dimensions/charge_density.h
index 81e1c7e5..4e2d58b5 100644
--- a/src/include/units/physical/dimensions/charge_density.h
+++ b/src/include/units/isq/dimensions/charge_density.h
@@ -23,10 +23,10 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/electric_charge.h>
-#include <units/physical/dimensions/length.h>
+#include <units/isq/dimensions/electric_charge.h>
+#include <units/isq/dimensions/length.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_electric_charge> Q, DimensionOfT<dim_length> L>
 struct dim_charge_density : derived_dimension<Child, U, exponent<Q, 1>, exponent<L, -3>> {};
@@ -40,4 +40,4 @@ concept ChargeDensity = QuantityOfT<T, dim_charge_density>;
 template<typename T>
 concept SurfaceChargeDensity = QuantityOfT<T, dim_surface_charge_density>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/concentration.h b/src/include/units/isq/dimensions/concentration.h
similarity index 89%
rename from src/include/units/physical/dimensions/concentration.h
rename to src/include/units/isq/dimensions/concentration.h
index b9ec9752..f1a82a08 100644
--- a/src/include/units/physical/dimensions/concentration.h
+++ b/src/include/units/isq/dimensions/concentration.h
@@ -23,10 +23,10 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/length.h>
-#include <units/physical/dimensions/amount_of_substance.h>
+#include <units/isq/dimensions/length.h>
+#include <units/isq/dimensions/amount_of_substance.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_amount_of_substance> M, DimensionOfT<dim_length> L>
 struct dim_concentration : derived_dimension<Child, U, exponent<M, 1>, exponent<L, -3>> {};
@@ -34,4 +34,4 @@ struct dim_concentration : derived_dimension<Child, U, exponent<M, 1>, exponent<
 template<typename T>
 concept Concentration = QuantityOfT<T, dim_concentration>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/conductance.h b/src/include/units/isq/dimensions/conductance.h
similarity index 92%
rename from src/include/units/physical/dimensions/conductance.h
rename to src/include/units/isq/dimensions/conductance.h
index f089b465..0dea42ff 100644
--- a/src/include/units/physical/dimensions/conductance.h
+++ b/src/include/units/isq/dimensions/conductance.h
@@ -23,9 +23,9 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/resistance.h>
+#include <units/isq/dimensions/resistance.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_resistance> R>
 struct dim_conductance : derived_dimension<Child, U, exponent<R, -1>> {};
@@ -33,4 +33,4 @@ struct dim_conductance : derived_dimension<Child, U, exponent<R, -1>> {};
 template<typename T>
 concept Conductance = QuantityOfT<T, dim_conductance>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/current_density.h b/src/include/units/isq/dimensions/current_density.h
similarity index 90%
rename from src/include/units/physical/dimensions/current_density.h
rename to src/include/units/isq/dimensions/current_density.h
index bcad7e87..e6e1420a 100644
--- a/src/include/units/physical/dimensions/current_density.h
+++ b/src/include/units/isq/dimensions/current_density.h
@@ -23,10 +23,10 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/electric_current.h>
-#include <units/physical/dimensions/length.h>
+#include <units/isq/dimensions/electric_current.h>
+#include <units/isq/dimensions/length.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_electric_current> I, DimensionOfT<dim_length> L>
 struct dim_current_density : derived_dimension<Child, U, exponent<I, 1>, exponent<L, -2>> {};
@@ -34,4 +34,4 @@ struct dim_current_density : derived_dimension<Child, U, exponent<I, 1>, exponen
 template<typename T>
 concept CurrentDensity = QuantityOfT<T, dim_current_density>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/density.h b/src/include/units/isq/dimensions/density.h
similarity index 90%
rename from src/include/units/physical/dimensions/density.h
rename to src/include/units/isq/dimensions/density.h
index f7834888..3b05b5ea 100644
--- a/src/include/units/physical/dimensions/density.h
+++ b/src/include/units/isq/dimensions/density.h
@@ -23,10 +23,10 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/length.h>
-#include <units/physical/dimensions/mass.h>
+#include <units/isq/dimensions/length.h>
+#include <units/isq/dimensions/mass.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_mass> M, DimensionOfT<dim_length> L>
 struct dim_density : derived_dimension<Child, U, exponent<M, 1>, exponent<L, -3>> {};
@@ -34,4 +34,4 @@ struct dim_density : derived_dimension<Child, U, exponent<M, 1>, exponent<L, -3>
 template<typename T>
 concept Density = QuantityOfT<T, dim_density>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/dynamic_viscosity.h b/src/include/units/isq/dimensions/dynamic_viscosity.h
similarity index 90%
rename from src/include/units/physical/dimensions/dynamic_viscosity.h
rename to src/include/units/isq/dimensions/dynamic_viscosity.h
index a35cf5cc..43add26c 100644
--- a/src/include/units/physical/dimensions/dynamic_viscosity.h
+++ b/src/include/units/isq/dimensions/dynamic_viscosity.h
@@ -23,10 +23,10 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/pressure.h>
-#include <units/physical/dimensions/time.h>
+#include <units/isq/dimensions/pressure.h>
+#include <units/isq/dimensions/time.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_pressure> P, DimensionOfT<dim_time> T>
 struct dim_dynamic_viscosity : derived_dimension<Child, U, exponent<P, 1>, exponent<T, 1>> {};
@@ -34,4 +34,4 @@ struct dim_dynamic_viscosity : derived_dimension<Child, U, exponent<P, 1>, expon
 template<typename T>
 concept DynamicViscosity = QuantityOfT<T, dim_dynamic_viscosity>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/electric_charge.h b/src/include/units/isq/dimensions/electric_charge.h
similarity index 90%
rename from src/include/units/physical/dimensions/electric_charge.h
rename to src/include/units/isq/dimensions/electric_charge.h
index cad8cf09..3f409c87 100644
--- a/src/include/units/physical/dimensions/electric_charge.h
+++ b/src/include/units/isq/dimensions/electric_charge.h
@@ -23,10 +23,10 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/electric_current.h>
-#include <units/physical/dimensions/time.h>
+#include <units/isq/dimensions/electric_current.h>
+#include <units/isq/dimensions/time.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_time> T, DimensionOfT<dim_electric_current> C>
 struct dim_electric_charge : derived_dimension<Child, U, exponent<T, 1>, exponent<C, 1>> {};
@@ -34,4 +34,4 @@ struct dim_electric_charge : derived_dimension<Child, U, exponent<T, 1>, exponen
 template<typename T>
 concept ElectricCharge = QuantityOfT<T, dim_electric_charge>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/electric_current.h b/src/include/units/isq/dimensions/electric_current.h
similarity index 95%
rename from src/include/units/physical/dimensions/electric_current.h
rename to src/include/units/isq/dimensions/electric_current.h
index 5540a4c5..52a3a4a1 100644
--- a/src/include/units/physical/dimensions/electric_current.h
+++ b/src/include/units/isq/dimensions/electric_current.h
@@ -24,7 +24,7 @@
 
 #include <units/concepts.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<Unit U>
 struct dim_electric_current : base_dimension<"I", U> {};
@@ -32,4 +32,4 @@ struct dim_electric_current : base_dimension<"I", U> {};
 template<typename T>
 concept ElectricCurrent = QuantityOfT<T, dim_electric_current>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/electric_field_strength.h b/src/include/units/isq/dimensions/electric_field_strength.h
similarity index 90%
rename from src/include/units/physical/dimensions/electric_field_strength.h
rename to src/include/units/isq/dimensions/electric_field_strength.h
index 7506378c..358e8203 100644
--- a/src/include/units/physical/dimensions/electric_field_strength.h
+++ b/src/include/units/isq/dimensions/electric_field_strength.h
@@ -23,10 +23,10 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/length.h>
-#include <units/physical/dimensions/voltage.h>
+#include <units/isq/dimensions/length.h>
+#include <units/isq/dimensions/voltage.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_voltage> V, DimensionOfT<dim_length> L>
 struct dim_electric_field_strength : derived_dimension<Child, U, exponent<V, 1>, exponent<L, -1>> {};
@@ -34,4 +34,4 @@ struct dim_electric_field_strength : derived_dimension<Child, U, exponent<V, 1>,
 template<typename T>
 concept ElectricFieldStrength = QuantityOfT<T, dim_electric_field_strength>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/energy.h b/src/include/units/isq/dimensions/energy.h
similarity index 90%
rename from src/include/units/physical/dimensions/energy.h
rename to src/include/units/isq/dimensions/energy.h
index 94bbeb87..1f88bc16 100644
--- a/src/include/units/physical/dimensions/energy.h
+++ b/src/include/units/isq/dimensions/energy.h
@@ -23,10 +23,10 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/force.h>
-#include <units/physical/dimensions/length.h>
+#include <units/isq/dimensions/force.h>
+#include <units/isq/dimensions/length.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_force> F, DimensionOfT<dim_length> L>
 struct dim_energy : derived_dimension<Child, U, exponent<F, 1>, exponent<L, 1>> {};
@@ -34,4 +34,4 @@ struct dim_energy : derived_dimension<Child, U, exponent<F, 1>, exponent<L, 1>>
 template<typename T>
 concept Energy = QuantityOfT<T, dim_energy>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/energy_density.h b/src/include/units/isq/dimensions/energy_density.h
similarity index 90%
rename from src/include/units/physical/dimensions/energy_density.h
rename to src/include/units/isq/dimensions/energy_density.h
index 44ba8722..41fe8a12 100644
--- a/src/include/units/physical/dimensions/energy_density.h
+++ b/src/include/units/isq/dimensions/energy_density.h
@@ -23,10 +23,10 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/energy.h>
-#include <units/physical/dimensions/volume.h>
+#include <units/isq/dimensions/energy.h>
+#include <units/isq/dimensions/volume.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_energy> E, DimensionOfT<dim_volume> V>
 struct dim_energy_density : derived_dimension<Child, U, exponent<E, 1>, exponent<V, -1>> {};
@@ -34,4 +34,4 @@ struct dim_energy_density : derived_dimension<Child, U, exponent<E, 1>, exponent
 template<typename T>
 concept EnergyDensity = QuantityOfT<T, dim_energy_density>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/force.h b/src/include/units/isq/dimensions/force.h
similarity index 90%
rename from src/include/units/physical/dimensions/force.h
rename to src/include/units/isq/dimensions/force.h
index e6504c99..92fdeb56 100644
--- a/src/include/units/physical/dimensions/force.h
+++ b/src/include/units/isq/dimensions/force.h
@@ -22,11 +22,11 @@
 
 #pragma once
 
-#include <units/physical/dimensions/acceleration.h>
+#include <units/isq/dimensions/acceleration.h>
 #include <units/concepts.h>
-#include <units/physical/dimensions/mass.h>
+#include <units/isq/dimensions/mass.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_mass> M, DimensionOfT<dim_acceleration> A>
 struct dim_force : derived_dimension<Child, U, exponent<M, 1>, exponent<A, 1>> {};
@@ -34,4 +34,4 @@ struct dim_force : derived_dimension<Child, U, exponent<M, 1>, exponent<A, 1>> {
 template<typename T>
 concept Force = QuantityOfT<T, dim_force>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/frequency.h b/src/include/units/isq/dimensions/frequency.h
similarity index 93%
rename from src/include/units/physical/dimensions/frequency.h
rename to src/include/units/isq/dimensions/frequency.h
index 6c33ee10..827e72c1 100644
--- a/src/include/units/physical/dimensions/frequency.h
+++ b/src/include/units/isq/dimensions/frequency.h
@@ -23,9 +23,9 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/time.h>
+#include <units/isq/dimensions/time.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_time> T>
 struct dim_frequency : derived_dimension<Child, U, exponent<T, -1>> {};
@@ -33,4 +33,4 @@ struct dim_frequency : derived_dimension<Child, U, exponent<T, -1>> {};
 template<typename T>
 concept Frequency = QuantityOfT<T, dim_frequency>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/heat_capacity.h b/src/include/units/isq/dimensions/heat_capacity.h
similarity index 88%
rename from src/include/units/physical/dimensions/heat_capacity.h
rename to src/include/units/isq/dimensions/heat_capacity.h
index 7d3068cb..c838491e 100644
--- a/src/include/units/physical/dimensions/heat_capacity.h
+++ b/src/include/units/isq/dimensions/heat_capacity.h
@@ -22,13 +22,13 @@
 
 #pragma once
 
-#include <units/physical/dimensions/amount_of_substance.h>
+#include <units/isq/dimensions/amount_of_substance.h>
 #include <units/concepts.h>
-#include <units/physical/dimensions/energy.h>
-#include <units/physical/dimensions/mass.h>
-#include <units/physical/dimensions/thermodynamic_temperature.h>
+#include <units/isq/dimensions/energy.h>
+#include <units/isq/dimensions/mass.h>
+#include <units/isq/dimensions/thermodynamic_temperature.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_energy> E, DimensionOfT<dim_thermodynamic_temperature> T>
 struct dim_heat_capacity : derived_dimension<Child, U, exponent<E, 1>, exponent<T, -1>> {};
@@ -48,4 +48,4 @@ concept SpecificHeatCapacity = QuantityOfT<T, dim_specific_heat_capacity>;
 template<typename T>
 concept MolarHeatCapacity = QuantityOfT<T, dim_molar_heat_capacity>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/inductance.h b/src/include/units/isq/dimensions/inductance.h
similarity index 89%
rename from src/include/units/physical/dimensions/inductance.h
rename to src/include/units/isq/dimensions/inductance.h
index 53a5f482..6e6ccbea 100644
--- a/src/include/units/physical/dimensions/inductance.h
+++ b/src/include/units/isq/dimensions/inductance.h
@@ -23,10 +23,10 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/electric_current.h>
-#include <units/physical/dimensions/magnetic_flux.h>
+#include <units/isq/dimensions/electric_current.h>
+#include <units/isq/dimensions/magnetic_flux.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_magnetic_flux> F, DimensionOfT<dim_electric_current> I>
 struct dim_inductance : derived_dimension<Child, U, exponent<F, 1>, exponent<I, -1>> {};
@@ -34,4 +34,4 @@ struct dim_inductance : derived_dimension<Child, U, exponent<F, 1>, exponent<I,
 template<typename T>
 concept Inductance = QuantityOfT<T, dim_inductance>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/length.h b/src/include/units/isq/dimensions/length.h
similarity index 95%
rename from src/include/units/physical/dimensions/length.h
rename to src/include/units/isq/dimensions/length.h
index 4460195d..39170399 100644
--- a/src/include/units/physical/dimensions/length.h
+++ b/src/include/units/isq/dimensions/length.h
@@ -24,7 +24,7 @@
 
 #include <units/concepts.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<Unit U>
 struct dim_length : base_dimension<"L", U> {};
@@ -32,4 +32,4 @@ struct dim_length : base_dimension<"L", U> {};
 template<typename T>
 concept Length = QuantityOfT<T, dim_length>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/luminance.h b/src/include/units/isq/dimensions/luminance.h
similarity index 89%
rename from src/include/units/physical/dimensions/luminance.h
rename to src/include/units/isq/dimensions/luminance.h
index 6fa966ed..6167591a 100644
--- a/src/include/units/physical/dimensions/luminance.h
+++ b/src/include/units/isq/dimensions/luminance.h
@@ -23,10 +23,10 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/luminous_intensity.h>
-#include <units/physical/dimensions/length.h>
+#include <units/isq/dimensions/luminous_intensity.h>
+#include <units/isq/dimensions/length.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_luminous_intensity> I, DimensionOfT<dim_length> L>
 struct dim_luminance : derived_dimension<Child, U, exponent<I, 1>, exponent<L, -2>> {};
@@ -34,4 +34,4 @@ struct dim_luminance : derived_dimension<Child, U, exponent<I, 1>, exponent<L, -
 template<typename T>
 concept Luminance = QuantityOfT<T, dim_luminance>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/luminous_intensity.h b/src/include/units/isq/dimensions/luminous_intensity.h
similarity index 95%
rename from src/include/units/physical/dimensions/luminous_intensity.h
rename to src/include/units/isq/dimensions/luminous_intensity.h
index c26b10a9..fb04a3fe 100644
--- a/src/include/units/physical/dimensions/luminous_intensity.h
+++ b/src/include/units/isq/dimensions/luminous_intensity.h
@@ -24,7 +24,7 @@
 
 #include <units/concepts.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<Unit U>
 struct dim_luminous_intensity : base_dimension<"J", U> {};
@@ -32,4 +32,4 @@ struct dim_luminous_intensity : base_dimension<"J", U> {};
 template<typename T>
 concept LuminousIntensity = QuantityOfT<T, dim_luminous_intensity>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/magnetic_flux.h b/src/include/units/isq/dimensions/magnetic_flux.h
similarity index 89%
rename from src/include/units/physical/dimensions/magnetic_flux.h
rename to src/include/units/isq/dimensions/magnetic_flux.h
index b39e29c1..2708d0d4 100644
--- a/src/include/units/physical/dimensions/magnetic_flux.h
+++ b/src/include/units/isq/dimensions/magnetic_flux.h
@@ -22,11 +22,11 @@
 
 #pragma once
 
-#include <units/physical/dimensions/area.h>
+#include <units/isq/dimensions/area.h>
 #include <units/concepts.h>
-#include <units/physical/dimensions/magnetic_induction.h>
+#include <units/isq/dimensions/magnetic_induction.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_magnetic_induction> B, DimensionOfT<dim_area> A>
 struct dim_magnetic_flux : derived_dimension<Child, U, exponent<B, 1>, exponent<A, 1>> {};
@@ -34,4 +34,4 @@ struct dim_magnetic_flux : derived_dimension<Child, U, exponent<B, 1>, exponent<
 template<typename T>
 concept MagneticFlux = QuantityOfT<T, dim_magnetic_flux>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/magnetic_induction.h b/src/include/units/isq/dimensions/magnetic_induction.h
similarity index 88%
rename from src/include/units/physical/dimensions/magnetic_induction.h
rename to src/include/units/isq/dimensions/magnetic_induction.h
index 579b3cd5..7bd59e41 100644
--- a/src/include/units/physical/dimensions/magnetic_induction.h
+++ b/src/include/units/isq/dimensions/magnetic_induction.h
@@ -23,11 +23,11 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/length.h>
-#include <units/physical/dimensions/time.h>
-#include <units/physical/dimensions/voltage.h>
+#include <units/isq/dimensions/length.h>
+#include <units/isq/dimensions/time.h>
+#include <units/isq/dimensions/voltage.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template <typename Child, Unit U, DimensionOfT<dim_voltage> V, DimensionOfT<dim_time> T, DimensionOfT<dim_length> L>
 struct dim_magnetic_induction : derived_dimension<Child, U, exponent<V, 1>, exponent<T, 1>, exponent<L, -2>> {};
@@ -35,4 +35,4 @@ struct dim_magnetic_induction : derived_dimension<Child, U, exponent<V, 1>, expo
 template<typename T>
 concept MagneticInduction = QuantityOfT<T, dim_magnetic_induction>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/mass.h b/src/include/units/isq/dimensions/mass.h
similarity index 95%
rename from src/include/units/physical/dimensions/mass.h
rename to src/include/units/isq/dimensions/mass.h
index d07c31eb..a2706b61 100644
--- a/src/include/units/physical/dimensions/mass.h
+++ b/src/include/units/isq/dimensions/mass.h
@@ -24,7 +24,7 @@
 
 #include <units/concepts.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<Unit U>
 struct dim_mass : base_dimension<"M", U> {};
@@ -32,4 +32,4 @@ struct dim_mass : base_dimension<"M", U> {};
 template<typename T>
 concept Mass = QuantityOfT<T, dim_mass>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/molar_energy.h b/src/include/units/isq/dimensions/molar_energy.h
similarity index 89%
rename from src/include/units/physical/dimensions/molar_energy.h
rename to src/include/units/isq/dimensions/molar_energy.h
index 57df33c4..b1c18e96 100644
--- a/src/include/units/physical/dimensions/molar_energy.h
+++ b/src/include/units/isq/dimensions/molar_energy.h
@@ -22,11 +22,11 @@
 
 #pragma once
 
-#include <units/physical/dimensions/amount_of_substance.h>
+#include <units/isq/dimensions/amount_of_substance.h>
 #include <units/concepts.h>
-#include <units/physical/dimensions/energy.h>
+#include <units/isq/dimensions/energy.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_energy> E, DimensionOfT<dim_amount_of_substance> M>
 struct dim_molar_energy : derived_dimension<Child, U, exponent<E, 1>, exponent<M, -1>> {};
@@ -34,4 +34,4 @@ struct dim_molar_energy : derived_dimension<Child, U, exponent<E, 1>, exponent<M
 template<typename T>
 concept MolarEnergy = QuantityOfT<T, dim_molar_energy>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/momentum.h b/src/include/units/isq/dimensions/momentum.h
similarity index 93%
rename from src/include/units/physical/dimensions/momentum.h
rename to src/include/units/isq/dimensions/momentum.h
index 309851df..5f3fad25 100644
--- a/src/include/units/physical/dimensions/momentum.h
+++ b/src/include/units/isq/dimensions/momentum.h
@@ -23,9 +23,9 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/speed.h>
+#include <units/isq/dimensions/speed.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_mass> M, DimensionOfT<dim_speed> V>
 struct dim_momentum : derived_dimension<Child, U, exponent<M, 1>, exponent<V, 1>> {};
@@ -33,4 +33,4 @@ struct dim_momentum : derived_dimension<Child, U, exponent<M, 1>, exponent<V, 1>
 template<typename T>
 concept Momentum = QuantityOfT<T, dim_momentum>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/permeability.h b/src/include/units/isq/dimensions/permeability.h
similarity index 90%
rename from src/include/units/physical/dimensions/permeability.h
rename to src/include/units/isq/dimensions/permeability.h
index af4d393d..8bd2da53 100644
--- a/src/include/units/physical/dimensions/permeability.h
+++ b/src/include/units/isq/dimensions/permeability.h
@@ -23,10 +23,10 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/inductance.h>
-#include <units/physical/dimensions/length.h>
+#include <units/isq/dimensions/inductance.h>
+#include <units/isq/dimensions/length.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_inductance> H, DimensionOfT<dim_length> L>
 struct dim_permeability : derived_dimension<Child, U, exponent<H, 1>, exponent<L, -1>> {};
@@ -34,4 +34,4 @@ struct dim_permeability : derived_dimension<Child, U, exponent<H, 1>, exponent<L
 template<typename T>
 concept Permeability = QuantityOfT<T, dim_permeability>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/permittivity.h b/src/include/units/isq/dimensions/permittivity.h
similarity index 90%
rename from src/include/units/physical/dimensions/permittivity.h
rename to src/include/units/isq/dimensions/permittivity.h
index e71d92bb..4d0cb155 100644
--- a/src/include/units/physical/dimensions/permittivity.h
+++ b/src/include/units/isq/dimensions/permittivity.h
@@ -22,11 +22,11 @@
 
 #pragma once
 
-#include <units/physical/dimensions/capacitance.h>
+#include <units/isq/dimensions/capacitance.h>
 #include <units/concepts.h>
-#include <units/physical/dimensions/length.h>
+#include <units/isq/dimensions/length.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_capacitance> C, DimensionOfT<dim_length> L>
 struct dim_permittivity : derived_dimension<Child, U, exponent<C, 1>, exponent<L, -1>> {};
@@ -34,4 +34,4 @@ struct dim_permittivity : derived_dimension<Child, U, exponent<C, 1>, exponent<L
 template<typename T>
 concept Permittivity = QuantityOfT<T, dim_permittivity>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/power.h b/src/include/units/isq/dimensions/power.h
similarity index 90%
rename from src/include/units/physical/dimensions/power.h
rename to src/include/units/isq/dimensions/power.h
index 9b0c7ed8..9bef0f74 100644
--- a/src/include/units/physical/dimensions/power.h
+++ b/src/include/units/isq/dimensions/power.h
@@ -23,10 +23,10 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/energy.h>
-#include <units/physical/dimensions/time.h>
+#include <units/isq/dimensions/energy.h>
+#include <units/isq/dimensions/time.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_energy> E, DimensionOfT<dim_time> T>
 struct dim_power : derived_dimension<Child, U, exponent<E, 1>, exponent<T, -1>> {};
@@ -34,4 +34,4 @@ struct dim_power : derived_dimension<Child, U, exponent<E, 1>, exponent<T, -1>>
 template<typename T>
 concept Power = QuantityOfT<T, dim_power>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/pressure.h b/src/include/units/isq/dimensions/pressure.h
similarity index 90%
rename from src/include/units/physical/dimensions/pressure.h
rename to src/include/units/isq/dimensions/pressure.h
index 8fe7f9a7..6f5f8934 100644
--- a/src/include/units/physical/dimensions/pressure.h
+++ b/src/include/units/isq/dimensions/pressure.h
@@ -22,11 +22,11 @@
 
 #pragma once
 
-#include <units/physical/dimensions/area.h>
+#include <units/isq/dimensions/area.h>
 #include <units/concepts.h>
-#include <units/physical/dimensions/force.h>
+#include <units/isq/dimensions/force.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_force> F, DimensionOfT<dim_area> A>
 struct dim_pressure : derived_dimension<Child, U, exponent<F, 1>, exponent<A, -1>> {};
@@ -34,4 +34,4 @@ struct dim_pressure : derived_dimension<Child, U, exponent<F, 1>, exponent<A, -1
 template<typename T>
 concept Pressure = QuantityOfT<T, dim_pressure>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/radioactivity.h b/src/include/units/isq/dimensions/radioactivity.h
similarity index 93%
rename from src/include/units/physical/dimensions/radioactivity.h
rename to src/include/units/isq/dimensions/radioactivity.h
index 3caa1c3a..3457153a 100644
--- a/src/include/units/physical/dimensions/radioactivity.h
+++ b/src/include/units/isq/dimensions/radioactivity.h
@@ -23,9 +23,9 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/time.h>
+#include <units/isq/dimensions/time.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_time> T>
 struct dim_radioactivity : derived_dimension<Child, U, exponent<T, -1>> {};
@@ -33,4 +33,4 @@ struct dim_radioactivity : derived_dimension<Child, U, exponent<T, -1>> {};
 template<typename T>
 concept Radioactivity = QuantityOfT<T, dim_radioactivity>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/resistance.h b/src/include/units/isq/dimensions/resistance.h
similarity index 89%
rename from src/include/units/physical/dimensions/resistance.h
rename to src/include/units/isq/dimensions/resistance.h
index e36180b0..7ec09111 100644
--- a/src/include/units/physical/dimensions/resistance.h
+++ b/src/include/units/isq/dimensions/resistance.h
@@ -23,10 +23,10 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/electric_current.h>
-#include <units/physical/dimensions/voltage.h>
+#include <units/isq/dimensions/electric_current.h>
+#include <units/isq/dimensions/voltage.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template <typename Child, Unit U, DimensionOfT<dim_voltage> V, DimensionOfT<dim_electric_current> C>
 struct dim_resistance : derived_dimension<Child,U, exponent<V, 1>, exponent<C, -1>> {};
@@ -34,4 +34,4 @@ struct dim_resistance : derived_dimension<Child,U, exponent<V, 1>, exponent<C, -
 template<typename T>
 concept Resistance = QuantityOfT<T, dim_resistance>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/speed.h b/src/include/units/isq/dimensions/speed.h
similarity index 90%
rename from src/include/units/physical/dimensions/speed.h
rename to src/include/units/isq/dimensions/speed.h
index 2a6ba185..e226fb04 100644
--- a/src/include/units/physical/dimensions/speed.h
+++ b/src/include/units/isq/dimensions/speed.h
@@ -23,10 +23,10 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/length.h>
-#include <units/physical/dimensions/time.h>
+#include <units/isq/dimensions/length.h>
+#include <units/isq/dimensions/time.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_length> L, DimensionOfT<dim_time> T>
 struct dim_speed : derived_dimension<Child, U, exponent<L, 1>, exponent<T, -1>> {};
@@ -34,4 +34,4 @@ struct dim_speed : derived_dimension<Child, U, exponent<L, 1>, exponent<T, -1>>
 template<typename T>
 concept Speed = QuantityOfT<T, dim_speed>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/surface_tension.h b/src/include/units/isq/dimensions/surface_tension.h
similarity index 90%
rename from src/include/units/physical/dimensions/surface_tension.h
rename to src/include/units/isq/dimensions/surface_tension.h
index 9b1a5f22..db46257a 100644
--- a/src/include/units/physical/dimensions/surface_tension.h
+++ b/src/include/units/isq/dimensions/surface_tension.h
@@ -23,10 +23,10 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/force.h>
-#include <units/physical/dimensions/length.h>
+#include <units/isq/dimensions/force.h>
+#include <units/isq/dimensions/length.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_force> F, DimensionOfT<dim_length> L>
 struct dim_surface_tension : derived_dimension<Child, U, exponent<F, 1>, exponent<L, -1>> {};
@@ -34,4 +34,4 @@ struct dim_surface_tension : derived_dimension<Child, U, exponent<F, 1>, exponen
 template<typename T>
 concept SurfaceTension = QuantityOfT<T, dim_surface_tension>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/thermal_conductivity.h b/src/include/units/isq/dimensions/thermal_conductivity.h
similarity index 87%
rename from src/include/units/physical/dimensions/thermal_conductivity.h
rename to src/include/units/isq/dimensions/thermal_conductivity.h
index 0123deee..b71c37af 100644
--- a/src/include/units/physical/dimensions/thermal_conductivity.h
+++ b/src/include/units/isq/dimensions/thermal_conductivity.h
@@ -23,11 +23,11 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/length.h>
-#include <units/physical/dimensions/power.h>
-#include <units/physical/dimensions/thermodynamic_temperature.h>
+#include <units/isq/dimensions/length.h>
+#include <units/isq/dimensions/power.h>
+#include <units/isq/dimensions/thermodynamic_temperature.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_power> P, DimensionOfT<dim_length> L, DimensionOfT<dim_thermodynamic_temperature> T>
 struct dim_thermal_conductivity : derived_dimension<Child, U, exponent<P, 1>, exponent<L, -1>, exponent<T, -1>> {};
@@ -35,4 +35,4 @@ struct dim_thermal_conductivity : derived_dimension<Child, U, exponent<P, 1>, ex
 template<typename T>
 concept ThermalConductivity = QuantityOfT<T, dim_thermal_conductivity>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/thermodynamic_temperature.h b/src/include/units/isq/dimensions/thermodynamic_temperature.h
similarity index 95%
rename from src/include/units/physical/dimensions/thermodynamic_temperature.h
rename to src/include/units/isq/dimensions/thermodynamic_temperature.h
index b0037682..8db16a23 100644
--- a/src/include/units/physical/dimensions/thermodynamic_temperature.h
+++ b/src/include/units/isq/dimensions/thermodynamic_temperature.h
@@ -24,7 +24,7 @@
 
 #include <units/concepts.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<Unit U>
 struct dim_thermodynamic_temperature : base_dimension<"Θ", U> {};
@@ -32,4 +32,4 @@ struct dim_thermodynamic_temperature : base_dimension<"Θ", U> {};
 template<typename T>
 concept ThermodynamicTemperature = QuantityOfT<T, dim_thermodynamic_temperature>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/time.h b/src/include/units/isq/dimensions/time.h
similarity index 95%
rename from src/include/units/physical/dimensions/time.h
rename to src/include/units/isq/dimensions/time.h
index 7f458983..f07b82d9 100644
--- a/src/include/units/physical/dimensions/time.h
+++ b/src/include/units/isq/dimensions/time.h
@@ -24,7 +24,7 @@
 
 #include <units/concepts.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<Unit U>
 struct dim_time : base_dimension<"T", U> {};
@@ -32,4 +32,4 @@ struct dim_time : base_dimension<"T", U> {};
 template<typename T>
 concept Time = QuantityOfT<T, dim_time>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/torque.h b/src/include/units/isq/dimensions/torque.h
similarity index 93%
rename from src/include/units/physical/dimensions/torque.h
rename to src/include/units/isq/dimensions/torque.h
index 01e103e3..0109b822 100644
--- a/src/include/units/physical/dimensions/torque.h
+++ b/src/include/units/isq/dimensions/torque.h
@@ -24,9 +24,9 @@
 
 #include <units/generic/angle.h>
 #include <units/concepts.h>
-#include <units/physical/dimensions/energy.h>
+#include <units/isq/dimensions/energy.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_force> F, DimensionOfT<dim_length> L, DimensionOfT<dim_angle> A>
 struct dim_torque : derived_dimension<Child, U, exponent<F, 1>, exponent<L, 1>, exponent<A, -1>> {};
@@ -34,4 +34,4 @@ struct dim_torque : derived_dimension<Child, U, exponent<F, 1>, exponent<L, 1>,
 template<typename T>
 concept Torque = QuantityOfT<T, dim_torque>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/voltage.h b/src/include/units/isq/dimensions/voltage.h
similarity index 89%
rename from src/include/units/physical/dimensions/voltage.h
rename to src/include/units/isq/dimensions/voltage.h
index c3f99d6e..fd0ba06b 100644
--- a/src/include/units/physical/dimensions/voltage.h
+++ b/src/include/units/isq/dimensions/voltage.h
@@ -23,10 +23,10 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/electric_current.h>
-#include <units/physical/dimensions/power.h>
+#include <units/isq/dimensions/electric_current.h>
+#include <units/isq/dimensions/power.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_power> P, DimensionOfT<dim_electric_current> C>
 struct dim_voltage : derived_dimension<Child, U, exponent<P, 1>, exponent<C, -1>> {};
@@ -34,4 +34,4 @@ struct dim_voltage : derived_dimension<Child, U, exponent<P, 1>, exponent<C, -1>
 template<typename T>
 concept Voltage = QuantityOfT<T, dim_voltage>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/dimensions/volume.h b/src/include/units/isq/dimensions/volume.h
similarity index 92%
rename from src/include/units/physical/dimensions/volume.h
rename to src/include/units/isq/dimensions/volume.h
index 62800ada..0972a00f 100644
--- a/src/include/units/physical/dimensions/volume.h
+++ b/src/include/units/isq/dimensions/volume.h
@@ -23,9 +23,9 @@
 #pragma once
 
 #include <units/concepts.h>
-#include <units/physical/dimensions/length.h>
+#include <units/isq/dimensions/length.h>
 
-namespace units::physical {
+namespace units::isq {
 
 template<typename Child, Unit U, DimensionOfT<dim_length> L>
 struct dim_volume : derived_dimension<Child, U, exponent<L, 3>> {};
@@ -33,4 +33,4 @@ struct dim_volume : derived_dimension<Child, U, exponent<L, 3>> {};
 template<typename T>
 concept Volume = QuantityOfT<T, dim_volume>;
 
-}  // namespace units::physical
+}  // namespace units::isq
diff --git a/src/include/units/physical/natural/bits/dimensions.h b/src/include/units/isq/natural/bits/dimensions.h
similarity index 71%
rename from src/include/units/physical/natural/bits/dimensions.h
rename to src/include/units/isq/natural/bits/dimensions.h
index 2067ecbf..bb9e8b45 100644
--- a/src/include/units/physical/natural/bits/dimensions.h
+++ b/src/include/units/isq/natural/bits/dimensions.h
@@ -22,45 +22,45 @@
 
 #pragma once
 
-#include <units/physical/dimensions.h>
-#include <units/physical/natural/bits/units.h>
+#include <units/isq/dimensions.h>
+#include <units/isq/natural/bits/units.h>
 #include <units/quantity.h>
 
-namespace units::physical::natural {
+namespace units::isq::natural {
 
-struct dim_length : physical::dim_length<inverted_gigaelectronvolt> {};
+struct dim_length : isq::dim_length<inverted_gigaelectronvolt> {};
 template<UnitOf<dim_length> U, QuantityValue Rep = double>
 using length = quantity<dim_length, U, Rep>;
 
-struct dim_time : physical::dim_time<inverted_gigaelectronvolt> {};
+struct dim_time : isq::dim_time<inverted_gigaelectronvolt> {};
 template<UnitOf<dim_time> U, QuantityValue Rep = double>
 using time = quantity<dim_time, U, Rep>;
 
-struct dim_mass : physical::dim_mass<gigaelectronvolt> {};
+struct dim_mass : isq::dim_mass<gigaelectronvolt> {};
 template<UnitOf<dim_mass> U, QuantityValue Rep = double>
 using mass = quantity<dim_mass, U, Rep>;
 
-struct dim_speed : physical::dim_speed<dim_speed, one, dim_length, dim_time> {};
+struct dim_speed : isq::dim_speed<dim_speed, one, dim_length, dim_time> {};
 template<UnitOf<dim_speed> U, QuantityValue Rep = double>
 using speed = quantity<dim_speed, U, Rep>;
 
-struct dim_acceleration : physical::dim_acceleration<dim_acceleration, gigaelectronvolt, dim_length, dim_time> {};
+struct dim_acceleration : isq::dim_acceleration<dim_acceleration, gigaelectronvolt, dim_length, dim_time> {};
 template<UnitOf<dim_acceleration> U, QuantityValue Rep = double>
 using acceleration = quantity<dim_acceleration, U, Rep>;
 
-struct dim_force : physical::dim_force<dim_force, square_gigaelectronvolt, dim_mass, dim_acceleration> {};
+struct dim_force : isq::dim_force<dim_force, square_gigaelectronvolt, dim_mass, dim_acceleration> {};
 template<UnitOf<dim_force> U, QuantityValue Rep = double>
 using force = quantity<dim_force, U, Rep>;
 
-struct dim_momentum : physical::dim_momentum<dim_momentum, gigaelectronvolt, dim_mass, dim_speed> {};
+struct dim_momentum : isq::dim_momentum<dim_momentum, gigaelectronvolt, dim_mass, dim_speed> {};
 template<UnitOf<dim_momentum> U, QuantityValue Rep = double>
 using momentum = quantity<dim_momentum, U, Rep>;
 
-struct dim_energy : physical::dim_energy<dim_energy, gigaelectronvolt, dim_force, dim_length> {};
+struct dim_energy : isq::dim_energy<dim_energy, gigaelectronvolt, dim_force, dim_length> {};
 template<UnitOf<dim_force> U, QuantityValue Rep = double>
 using energy = quantity<dim_force, U, Rep>;
 
 // Typical UDLs will not work here as the same units are reused by many quantities.
 // Should we define some strange ones (i.e. _q_mass_GeV)?
 
-}  // namespace units::physical::natural
+}  // namespace units::isq::natural
diff --git a/src/include/units/physical/natural/bits/units.h b/src/include/units/isq/natural/bits/units.h
similarity index 93%
rename from src/include/units/physical/natural/bits/units.h
rename to src/include/units/isq/natural/bits/units.h
index ec42e1f0..837a0c80 100644
--- a/src/include/units/physical/natural/bits/units.h
+++ b/src/include/units/isq/natural/bits/units.h
@@ -23,9 +23,9 @@
 #pragma once
 
 #include <units/unit.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/si/prefixes.h>
 
-namespace units::physical::natural {
+namespace units::isq::natural {
 
 struct electronvolt : named_unit<electronvolt, "eV", si::prefix> {};
 struct gigaelectronvolt : prefixed_unit<gigaelectronvolt, si::giga, electronvolt> {};
@@ -37,4 +37,4 @@ struct square_gigaelectronvolt : named_unit<square_gigaelectronvolt, basic_symbo
 // natural units as an isolated island with ev = 1 which simplifies all
 // the maths a lot?
 
-}  // namespace units::physical::natural
+}  // namespace units::isq::natural
diff --git a/src/include/units/physical/natural/constants.h b/src/include/units/isq/natural/constants.h
similarity index 90%
rename from src/include/units/physical/natural/constants.h
rename to src/include/units/isq/natural/constants.h
index 43f3c961..b681bafe 100644
--- a/src/include/units/physical/natural/constants.h
+++ b/src/include/units/isq/natural/constants.h
@@ -22,11 +22,11 @@
 
 #pragma once
 
-#include <units/physical/natural/bits/dimensions.h>
+#include <units/isq/natural/bits/dimensions.h>
 
-namespace units::physical::natural {
+namespace units::isq::natural {
 
 template<QuantityValue Rep = double>
 inline constexpr auto speed_of_light = speed<one, Rep>(1);
 
-}  // namespace units::physical::natural
+}  // namespace units::isq::natural
diff --git a/src/include/units/physical/natural/natural.h b/src/include/units/isq/natural/natural.h
similarity index 100%
rename from src/include/units/physical/natural/natural.h
rename to src/include/units/isq/natural/natural.h
diff --git a/src/include/units/physical/si/absorbed_dose.h b/src/include/units/isq/si/absorbed_dose.h
similarity index 97%
rename from src/include/units/physical/si/absorbed_dose.h
rename to src/include/units/isq/si/absorbed_dose.h
index 81a07ec5..6dfcb6fe 100644
--- a/src/include/units/physical/si/absorbed_dose.h
+++ b/src/include/units/isq/si/absorbed_dose.h
@@ -22,12 +22,12 @@
 
 #pragma once
 
-#include <units/physical/dimensions/absorbed_dose.h>
-#include <units/physical/si/energy.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/absorbed_dose.h>
+#include <units/isq/si/energy.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct gray : named_unit<gray, "Gy", prefix> {};
 struct yoctogray : prefixed_unit<yoctogray, yocto, gray> {};
@@ -51,7 +51,7 @@ struct exagray : prefixed_unit<exagray, exa, gray> {};
 struct zettagray : prefixed_unit<zettagray, zetta, gray> {};
 struct yottagray : prefixed_unit<yottagray, yotta, gray> {};
 
-struct dim_absorbed_dose : physical::dim_absorbed_dose<dim_absorbed_dose, gray, dim_energy, dim_mass> {};
+struct dim_absorbed_dose : isq::dim_absorbed_dose<dim_absorbed_dose, gray, dim_energy, dim_mass> {};
 
 template<UnitOf<dim_absorbed_dose> U, QuantityValue Rep = double>
 using absorbed_dose = quantity<dim_absorbed_dose, U, Rep>;
@@ -170,4 +170,4 @@ inline constexpr auto YGy = absorbed_dose<yottagray, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/acceleration.h b/src/include/units/isq/si/acceleration.h
similarity index 86%
rename from src/include/units/physical/si/acceleration.h
rename to src/include/units/isq/si/acceleration.h
index 94934ac8..97db148d 100644
--- a/src/include/units/physical/si/acceleration.h
+++ b/src/include/units/isq/si/acceleration.h
@@ -22,14 +22,14 @@
 
 #pragma once
 
-#include <units/physical/dimensions/acceleration.h>
-#include <units/physical/si/speed.h>
+#include <units/isq/dimensions/acceleration.h>
+#include <units/isq/si/speed.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct metre_per_second_sq : unit<metre_per_second_sq> {};
-struct dim_acceleration : physical::dim_acceleration<dim_acceleration, metre_per_second_sq, dim_length, dim_time> {};
+struct dim_acceleration : isq::dim_acceleration<dim_acceleration, metre_per_second_sq, dim_length, dim_time> {};
 
 template<UnitOf<dim_acceleration> U, QuantityValue Rep = double>
 using acceleration = quantity<dim_acceleration, U, Rep>;
@@ -42,4 +42,4 @@ constexpr auto operator"" _q_m_per_s2(long double l) { return acceleration<metre
 
 }  // namespace literals
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/amount_of_substance.h b/src/include/units/isq/si/amount_of_substance.h
similarity index 88%
rename from src/include/units/physical/si/amount_of_substance.h
rename to src/include/units/isq/si/amount_of_substance.h
index f4cc8ccb..97253924 100644
--- a/src/include/units/physical/si/amount_of_substance.h
+++ b/src/include/units/isq/si/amount_of_substance.h
@@ -23,15 +23,15 @@
 #pragma once
 
 #include <units/one_rep.h>
-#include <units/physical/dimensions/amount_of_substance.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/amount_of_substance.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct mole : named_unit<mole, "mol", prefix> {};
 
-struct dim_amount_of_substance : physical::dim_amount_of_substance<mole> {};
+struct dim_amount_of_substance : isq::dim_amount_of_substance<mole> {};
 
 template<UnitOf<dim_amount_of_substance> U, QuantityValue Rep = double>
 using amount_of_substance = quantity<dim_amount_of_substance, U, Rep>;
@@ -50,4 +50,4 @@ inline constexpr auto mol = amount_of_substance<mole, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/angular_velocity.h b/src/include/units/isq/si/angular_velocity.h
similarity index 86%
rename from src/include/units/physical/si/angular_velocity.h
rename to src/include/units/isq/si/angular_velocity.h
index f10136c4..9d59bb85 100644
--- a/src/include/units/physical/si/angular_velocity.h
+++ b/src/include/units/isq/si/angular_velocity.h
@@ -22,17 +22,17 @@
 
 #pragma once
 
-#include <units/physical/dimensions/angular_velocity.h>
+#include <units/isq/dimensions/angular_velocity.h>
 #include <units/generic/angle.h>
-#include <units/physical/si/time.h>
+#include <units/isq/si/time.h>
 
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct radian_per_second : named_unit<radian_per_second, basic_symbol_text{"ω", "w"}, no_prefix> {};
 
-struct dim_angular_velocity : physical::dim_angular_velocity<dim_angular_velocity, radian_per_second, dim_angle<>, dim_time> {};
+struct dim_angular_velocity : isq::dim_angular_velocity<dim_angular_velocity, radian_per_second, dim_angle<>, dim_time> {};
 
 template<UnitOf<dim_angular_velocity> U, QuantityValue Rep = double>
 using angular_velocity = quantity<dim_angular_velocity, U, Rep>;
@@ -45,4 +45,4 @@ constexpr auto operator"" _q_rad_per_s(long double l) { return angular_velocity<
 
 }  // namespace literals
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/area.h b/src/include/units/isq/si/area.h
similarity index 97%
rename from src/include/units/physical/si/area.h
rename to src/include/units/isq/si/area.h
index 3907e11a..eea66da3 100644
--- a/src/include/units/physical/si/area.h
+++ b/src/include/units/isq/si/area.h
@@ -22,14 +22,14 @@
 
 #pragma once
 
-#include <units/physical/dimensions/area.h>
-#include <units/physical/si/length.h>
+#include <units/isq/dimensions/area.h>
+#include <units/isq/si/length.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct square_metre : unit<square_metre> {};
-struct dim_area : physical::dim_area<dim_area, square_metre, dim_length> {};
+struct dim_area : isq::dim_area<dim_area, square_metre, dim_length> {};
 
 struct square_yoctometre : deduced_unit<square_yoctometre, dim_area, yoctometre> {};
 struct square_zeptometre : deduced_unit<square_zeptometre, dim_area, zeptometre> {};
@@ -176,4 +176,4 @@ inline constexpr auto ha = area<hectare, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/capacitance.h b/src/include/units/isq/si/capacitance.h
similarity index 96%
rename from src/include/units/physical/si/capacitance.h
rename to src/include/units/isq/si/capacitance.h
index c057ddb5..d37b92e9 100644
--- a/src/include/units/physical/si/capacitance.h
+++ b/src/include/units/isq/si/capacitance.h
@@ -22,13 +22,13 @@
 
 #pragma once
 
-#include <units/physical/dimensions/capacitance.h>
-#include <units/physical/si/electric_charge.h>
-#include <units/physical/si/voltage.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/capacitance.h>
+#include <units/isq/si/electric_charge.h>
+#include <units/isq/si/voltage.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct farad : named_unit<farad, "F", prefix> {};
 struct yoctofarad : prefixed_unit<yoctofarad, yocto, farad> {};
@@ -52,7 +52,7 @@ struct exafarad : prefixed_unit<exafarad, exa, farad> {};
 struct zettafarad : prefixed_unit<zettafarad, zetta, farad> {};
 struct yottafarad : prefixed_unit<yottafarad, yotta, farad> {};
 
-struct dim_capacitance : physical::dim_capacitance<dim_capacitance, farad, dim_electric_charge, dim_voltage> {};
+struct dim_capacitance : isq::dim_capacitance<dim_capacitance, farad, dim_electric_charge, dim_voltage> {};
 
 template<UnitOf<dim_capacitance> U, QuantityValue Rep = double>
 using capacitance = quantity<dim_capacitance, U, Rep>;
@@ -171,4 +171,4 @@ inline constexpr auto YF = capacitance<yottafarad, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/catalytic_activity.h b/src/include/units/isq/si/catalytic_activity.h
similarity index 96%
rename from src/include/units/physical/si/catalytic_activity.h
rename to src/include/units/isq/si/catalytic_activity.h
index 5887530c..ae1e0ac5 100644
--- a/src/include/units/physical/si/catalytic_activity.h
+++ b/src/include/units/isq/si/catalytic_activity.h
@@ -22,13 +22,13 @@
 
 #pragma once
 
-#include <units/physical/dimensions/catalytic_activity.h>
-#include <units/physical/si/amount_of_substance.h>
-#include <units/physical/si/time.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/catalytic_activity.h>
+#include <units/isq/si/amount_of_substance.h>
+#include <units/isq/si/time.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct katal : named_unit<katal, "kat", prefix> {};
 struct yoctokatal : prefixed_unit<yoctokatal, yocto, katal> {};
@@ -54,7 +54,7 @@ struct yottakatal : prefixed_unit<yottakatal, yotta, katal> {};
 
 struct enzyme_unit : named_scaled_unit<enzyme_unit, "U", prefix, ratio(1, 60, -6), katal> {};
 
-struct dim_catalytic_activity : physical::dim_catalytic_activity<dim_catalytic_activity, katal, dim_time, dim_amount_of_substance> {};
+struct dim_catalytic_activity : isq::dim_catalytic_activity<dim_catalytic_activity, katal, dim_time, dim_amount_of_substance> {};
 
 template<UnitOf<dim_catalytic_activity> U, QuantityValue Rep = double>
 using catalytic_activity = quantity<dim_catalytic_activity, U, Rep>;
@@ -178,5 +178,5 @@ inline constexpr auto U = catalytic_activity<enzyme_unit, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
 
diff --git a/src/include/units/physical/si/cgs/acceleration.h b/src/include/units/isq/si/cgs/acceleration.h
similarity index 86%
rename from src/include/units/physical/si/cgs/acceleration.h
rename to src/include/units/isq/si/cgs/acceleration.h
index bd9503f7..a0e2313a 100644
--- a/src/include/units/physical/si/cgs/acceleration.h
+++ b/src/include/units/isq/si/cgs/acceleration.h
@@ -22,14 +22,14 @@
 
 #pragma once
 
-#include <units/physical/dimensions/acceleration.h>
-#include <units/physical/si/cgs/speed.h>
+#include <units/isq/dimensions/acceleration.h>
+#include <units/isq/si/cgs/speed.h>
 #include <units/quantity.h>
 
-namespace units::physical::si::cgs {
+namespace units::isq::si::cgs {
 
 struct gal : named_unit<gal, "Gal", si::prefix> {};
-struct dim_acceleration : physical::dim_acceleration<dim_acceleration, gal, dim_length, dim_time> {};
+struct dim_acceleration : isq::dim_acceleration<dim_acceleration, gal, dim_length, dim_time> {};
 
 template<UnitOf<dim_acceleration> U, QuantityValue Rep = double>
 using acceleration = quantity<dim_acceleration, U, Rep>;
@@ -48,4 +48,4 @@ inline constexpr auto Gal = acceleration<gal, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::cgs
+}  // namespace units::isq::si::cgs
diff --git a/src/include/units/physical/si/cgs/area.h b/src/include/units/isq/si/cgs/area.h
similarity index 88%
rename from src/include/units/physical/si/cgs/area.h
rename to src/include/units/isq/si/cgs/area.h
index 632bdcd5..39cdd645 100644
--- a/src/include/units/physical/si/cgs/area.h
+++ b/src/include/units/isq/si/cgs/area.h
@@ -22,15 +22,15 @@
 
 #pragma once
 
-#include <units/physical/si/area.h>
-#include <units/physical/si/cgs/length.h>
+#include <units/isq/si/area.h>
+#include <units/isq/si/cgs/length.h>
 #include <units/quantity.h>
 
-namespace units::physical::si::cgs {
+namespace units::isq::si::cgs {
 
 using si::square_centimetre;
 
-struct dim_area : physical::dim_area<dim_area, square_centimetre, dim_length> {};
+struct dim_area : isq::dim_area<dim_area, square_centimetre, dim_length> {};
 
 template<UnitOf<dim_area> U, QuantityValue Rep = double>
 using area = quantity<dim_area, U, Rep>;
@@ -49,4 +49,4 @@ inline constexpr auto cm2 = area<square_centimetre, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::cgs
+}  // namespace units::isq::si::cgs
diff --git a/src/include/units/isq/si/cgs/cgs.h b/src/include/units/isq/si/cgs/cgs.h
new file mode 100644
index 00000000..2f4723f7
--- /dev/null
+++ b/src/include/units/isq/si/cgs/cgs.h
@@ -0,0 +1,35 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2018 Mateusz Pusz
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#pragma once
+
+#include <units/isq/si/cgs/length.h>
+#include <units/isq/si/cgs/mass.h>
+#include <units/isq/si/cgs/time.h>
+
+#include <units/isq/si/cgs/acceleration.h>
+#include <units/isq/si/cgs/area.h>
+#include <units/isq/si/cgs/energy.h>
+#include <units/isq/si/cgs/force.h>
+#include <units/isq/si/cgs/power.h>
+#include <units/isq/si/cgs/pressure.h>
+#include <units/isq/si/cgs/speed.h>
diff --git a/src/include/units/physical/si/cgs/energy.h b/src/include/units/isq/si/cgs/energy.h
similarity index 86%
rename from src/include/units/physical/si/cgs/energy.h
rename to src/include/units/isq/si/cgs/energy.h
index 9269577f..8141a945 100644
--- a/src/include/units/physical/si/cgs/energy.h
+++ b/src/include/units/isq/si/cgs/energy.h
@@ -22,16 +22,16 @@
 
 #pragma once
 
-#include <units/physical/dimensions/energy.h>
-#include <units/physical/si/cgs/force.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/energy.h>
+#include <units/isq/si/cgs/force.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si::cgs {
+namespace units::isq::si::cgs {
 
 struct erg : named_unit<erg, "erg", si::prefix> {};
 
-struct dim_energy : physical::dim_energy<dim_energy, erg, dim_force, dim_length> {};
+struct dim_energy : isq::dim_energy<dim_energy, erg, dim_force, dim_length> {};
 
 template<UnitOf<dim_energy> U, QuantityValue Rep = double>
 using energy = quantity<dim_energy, U, Rep>;
@@ -50,4 +50,4 @@ inline constexpr auto erg = energy<cgs::erg, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::cgs
+}  // namespace units::isq::si::cgs
diff --git a/src/include/units/physical/si/cgs/force.h b/src/include/units/isq/si/cgs/force.h
similarity index 83%
rename from src/include/units/physical/si/cgs/force.h
rename to src/include/units/isq/si/cgs/force.h
index 32bea9d8..ac605e1f 100644
--- a/src/include/units/physical/si/cgs/force.h
+++ b/src/include/units/isq/si/cgs/force.h
@@ -22,17 +22,17 @@
 
 #pragma once
 
-#include <units/physical/dimensions/force.h>
-#include <units/physical/si/cgs/acceleration.h>
-#include <units/physical/si/cgs/mass.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/force.h>
+#include <units/isq/si/cgs/acceleration.h>
+#include <units/isq/si/cgs/mass.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si::cgs {
+namespace units::isq::si::cgs {
 
 struct dyne : named_unit<dyne, "dyn", si::prefix> {};
 
-struct dim_force : physical::dim_force<dim_force, dyne, dim_mass, dim_acceleration> {};
+struct dim_force : isq::dim_force<dim_force, dyne, dim_mass, dim_acceleration> {};
 
 template<UnitOf<dim_force> U, QuantityValue Rep = double>
 using force = quantity<dim_force, U, Rep>;
@@ -51,4 +51,4 @@ inline constexpr auto dyn = force<dyne, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::cgs
+}  // namespace units::isq::si::cgs
diff --git a/src/include/units/physical/si/cgs/length.h b/src/include/units/isq/si/cgs/length.h
similarity index 91%
rename from src/include/units/physical/si/cgs/length.h
rename to src/include/units/isq/si/cgs/length.h
index ab06c53d..633f2867 100644
--- a/src/include/units/physical/si/cgs/length.h
+++ b/src/include/units/isq/si/cgs/length.h
@@ -22,14 +22,14 @@
 
 #pragma once
 
-#include <units/physical/si/length.h>
+#include <units/isq/si/length.h>
 #include <units/quantity.h>
 
-namespace units::physical::si::cgs {
+namespace units::isq::si::cgs {
 
 using si::centimetre;
 
-struct dim_length : physical::dim_length<centimetre> {};
+struct dim_length : isq::dim_length<centimetre> {};
 
 template<UnitOf<dim_length> U, QuantityValue Rep = double>
 using length = quantity<dim_length, U, Rep>;
@@ -48,4 +48,4 @@ inline constexpr auto cm = length<centimetre, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::cgs
+}  // namespace units::isq::si::cgs
diff --git a/src/include/units/physical/si/cgs/mass.h b/src/include/units/isq/si/cgs/mass.h
similarity index 91%
rename from src/include/units/physical/si/cgs/mass.h
rename to src/include/units/isq/si/cgs/mass.h
index f88b95e4..05aa2fc7 100644
--- a/src/include/units/physical/si/cgs/mass.h
+++ b/src/include/units/isq/si/cgs/mass.h
@@ -22,14 +22,14 @@
 
 #pragma once
 
-#include <units/physical/si/mass.h>
+#include <units/isq/si/mass.h>
 #include <units/quantity.h>
 
-namespace units::physical::si::cgs {
+namespace units::isq::si::cgs {
 
 using si::gram;
 
-struct dim_mass : physical::dim_mass<gram> {};
+struct dim_mass : isq::dim_mass<gram> {};
 
 template<UnitOf<dim_mass> U, QuantityValue Rep = double>
 using mass = quantity<dim_mass, U, Rep>;
@@ -48,4 +48,4 @@ inline constexpr auto g = mass<gram, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::cgs
+}  // namespace units::isq::si::cgs
diff --git a/src/include/units/physical/si/cgs/power.h b/src/include/units/isq/si/cgs/power.h
similarity index 85%
rename from src/include/units/physical/si/cgs/power.h
rename to src/include/units/isq/si/cgs/power.h
index b1838b65..2adec6e6 100644
--- a/src/include/units/physical/si/cgs/power.h
+++ b/src/include/units/isq/si/cgs/power.h
@@ -22,16 +22,16 @@
 
 #pragma once
 
-#include <units/physical/dimensions/power.h>
-#include <units/physical/si/cgs/energy.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/power.h>
+#include <units/isq/si/cgs/energy.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si::cgs {
+namespace units::isq::si::cgs {
 
 struct erg_per_second : unit<erg_per_second> {};
 
-struct dim_power : physical::dim_power<dim_power, erg_per_second, dim_energy, dim_time> {};
+struct dim_power : isq::dim_power<dim_power, erg_per_second, dim_energy, dim_time> {};
 
 template<UnitOf<dim_power> U, QuantityValue Rep = double>
 using power = quantity<dim_power, U, Rep>;
@@ -44,4 +44,4 @@ constexpr auto operator"" _q_erg_per_s(long double l) { return power<erg_per_sec
 
 }  // namespace literals
 
-}  // namespace units::physical::si::cgs
+}  // namespace units::isq::si::cgs
diff --git a/src/include/units/physical/si/cgs/pressure.h b/src/include/units/isq/si/cgs/pressure.h
similarity index 84%
rename from src/include/units/physical/si/cgs/pressure.h
rename to src/include/units/isq/si/cgs/pressure.h
index bfa5c07f..37ebf77e 100644
--- a/src/include/units/physical/si/cgs/pressure.h
+++ b/src/include/units/isq/si/cgs/pressure.h
@@ -22,17 +22,17 @@
 
 #pragma once
 
-#include <units/physical/dimensions/pressure.h>
-#include <units/physical/si/cgs/area.h>
-#include <units/physical/si/cgs/force.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/pressure.h>
+#include <units/isq/si/cgs/area.h>
+#include <units/isq/si/cgs/force.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si::cgs {
+namespace units::isq::si::cgs {
 
 struct barye : named_unit<barye, "Ba", si::prefix> {};
 
-struct dim_pressure : physical::dim_pressure<dim_pressure, barye, dim_force, dim_area> {};
+struct dim_pressure : isq::dim_pressure<dim_pressure, barye, dim_force, dim_area> {};
 
 template<UnitOf<dim_pressure> U, QuantityValue Rep = double>
 using pressure = quantity<dim_pressure, U, Rep>;
@@ -51,4 +51,4 @@ inline constexpr auto Ba = pressure<barye, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::cgs
+}  // namespace units::isq::si::cgs
diff --git a/src/include/units/physical/si/cgs/speed.h b/src/include/units/isq/si/cgs/speed.h
similarity index 84%
rename from src/include/units/physical/si/cgs/speed.h
rename to src/include/units/isq/si/cgs/speed.h
index 1e363bc4..89c048b4 100644
--- a/src/include/units/physical/si/cgs/speed.h
+++ b/src/include/units/isq/si/cgs/speed.h
@@ -22,15 +22,15 @@
 
 #pragma once
 
-#include <units/physical/dimensions/speed.h>
-#include <units/physical/si/cgs/length.h>
-#include <units/physical/si/cgs/time.h>
+#include <units/isq/dimensions/speed.h>
+#include <units/isq/si/cgs/length.h>
+#include <units/isq/si/cgs/time.h>
 #include <units/quantity.h>
 
-namespace units::physical::si::cgs {
+namespace units::isq::si::cgs {
 
 struct centimetre_per_second : unit<centimetre_per_second> {};
-struct dim_speed : physical::dim_speed<dim_speed, centimetre_per_second, dim_length, dim_time> {};
+struct dim_speed : isq::dim_speed<dim_speed, centimetre_per_second, dim_length, dim_time> {};
 
 template<UnitOf<dim_speed> U, QuantityValue Rep = double>
 using speed = quantity<dim_speed, U, Rep>;
@@ -43,4 +43,4 @@ constexpr auto operator"" _q_cm_per_s(long double l) { return speed<centimetre_p
 
 }  // namespace literals
 
-}  // namespace units::physical::si::cgs
+}  // namespace units::isq::si::cgs
diff --git a/src/include/units/physical/si/cgs/time.h b/src/include/units/isq/si/cgs/time.h
similarity index 92%
rename from src/include/units/physical/si/cgs/time.h
rename to src/include/units/isq/si/cgs/time.h
index 7c9fbf41..bcb3e72f 100644
--- a/src/include/units/physical/si/cgs/time.h
+++ b/src/include/units/isq/si/cgs/time.h
@@ -22,10 +22,10 @@
 
 #pragma once
 
-#include <units/physical/si/time.h>
+#include <units/isq/si/time.h>
 #include <units/quantity.h>
 
-namespace units::physical::si::cgs {
+namespace units::isq::si::cgs {
 
 using si::second;
 
@@ -44,4 +44,4 @@ using si::unit_constants::s;
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::cgs
+}  // namespace units::isq::si::cgs
diff --git a/src/include/units/physical/si/charge_density.h b/src/include/units/isq/si/charge_density.h
similarity index 81%
rename from src/include/units/physical/si/charge_density.h
rename to src/include/units/isq/si/charge_density.h
index 8e9e0538..98fd5276 100644
--- a/src/include/units/physical/si/charge_density.h
+++ b/src/include/units/isq/si/charge_density.h
@@ -22,19 +22,19 @@
 
 #pragma once
 
-#include <units/physical/dimensions/charge_density.h>
-#include <units/physical/si/electric_charge.h>
-#include <units/physical/si/length.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/charge_density.h>
+#include <units/isq/si/electric_charge.h>
+#include <units/isq/si/length.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct coulomb_per_metre_cub : unit<coulomb_per_metre_cub> {};
 struct coulomb_per_metre_sq : unit<coulomb_per_metre_sq> {};
 
-struct dim_charge_density : physical::dim_charge_density<dim_charge_density, coulomb_per_metre_cub, dim_electric_charge, dim_length> {};
-struct dim_surface_charge_density : physical::dim_surface_charge_density<dim_surface_charge_density, coulomb_per_metre_sq, dim_electric_charge, dim_length> {};
+struct dim_charge_density : isq::dim_charge_density<dim_charge_density, coulomb_per_metre_cub, dim_electric_charge, dim_length> {};
+struct dim_surface_charge_density : isq::dim_surface_charge_density<dim_surface_charge_density, coulomb_per_metre_sq, dim_electric_charge, dim_length> {};
 
 template<UnitOf<dim_charge_density> U, QuantityValue Rep = double>
 using charge_density = quantity<dim_charge_density, U, Rep>;
@@ -54,4 +54,4 @@ constexpr auto operator"" _q_C_per_m2(long double l) { return surface_charge_den
 
 }  // namespace literals
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/concentration.h b/src/include/units/isq/si/concentration.h
similarity index 83%
rename from src/include/units/physical/si/concentration.h
rename to src/include/units/isq/si/concentration.h
index f6e27cba..70544d8f 100644
--- a/src/include/units/physical/si/concentration.h
+++ b/src/include/units/isq/si/concentration.h
@@ -22,15 +22,15 @@
 
 #pragma once
 
-#include <units/physical/dimensions/concentration.h>
-#include <units/physical/si/length.h>
-#include <units/physical/si/amount_of_substance.h>
+#include <units/isq/dimensions/concentration.h>
+#include <units/isq/si/length.h>
+#include <units/isq/si/amount_of_substance.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct mol_per_metre_cub : unit<mol_per_metre_cub> {};
-struct dim_concentration : physical::dim_concentration<dim_concentration, mol_per_metre_cub, dim_amount_of_substance, dim_length> {};
+struct dim_concentration : isq::dim_concentration<dim_concentration, mol_per_metre_cub, dim_amount_of_substance, dim_length> {};
 
 template<UnitOf<dim_concentration> U, QuantityValue Rep = double>
 using concentration = quantity<dim_concentration, U, Rep>;
@@ -43,5 +43,5 @@ constexpr auto operator"" _q_mol_per_m3(long double l) { return concentration<mo
 
 }  // namespace literals
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
 
diff --git a/src/include/units/physical/si/conductance.h b/src/include/units/isq/si/conductance.h
similarity index 96%
rename from src/include/units/physical/si/conductance.h
rename to src/include/units/isq/si/conductance.h
index 2b0f9113..061964f0 100644
--- a/src/include/units/physical/si/conductance.h
+++ b/src/include/units/isq/si/conductance.h
@@ -22,12 +22,12 @@
 
 #pragma once
 
-#include <units/physical/dimensions/conductance.h>
-#include <units/physical/si/resistance.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/conductance.h>
+#include <units/isq/si/resistance.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct siemens : named_unit<siemens, "S", prefix> {};
 struct yoctosiemens : prefixed_unit<yoctosiemens, yocto, siemens> {};
@@ -47,7 +47,7 @@ struct exasiemens : prefixed_unit<exasiemens, exa, siemens> {};
 struct zettasiemens : prefixed_unit<zettasiemens, zetta, siemens> {};
 struct yottasiemens : prefixed_unit<yottasiemens, yotta, siemens> {};
 
-struct dim_conductance : physical::dim_conductance<dim_conductance, siemens, dim_resistance> {};
+struct dim_conductance : isq::dim_conductance<dim_conductance, siemens, dim_resistance> {};
 
 template<UnitOf<dim_conductance> U, QuantityValue Rep = double>
 using conductance = quantity<dim_conductance, U, Rep>;
@@ -146,5 +146,5 @@ inline constexpr auto YS = conductance<yottasiemens, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
 
diff --git a/src/include/units/physical/si/constants.h b/src/include/units/isq/si/constants.h
similarity index 85%
rename from src/include/units/physical/si/constants.h
rename to src/include/units/isq/si/constants.h
index 1aef9240..0c8f7610 100644
--- a/src/include/units/physical/si/constants.h
+++ b/src/include/units/isq/si/constants.h
@@ -22,15 +22,15 @@
 
 #pragma once
 
-#include <units/physical/si/amount_of_substance.h>
-#include <units/physical/si/thermodynamic_temperature.h>
-#include <units/physical/si/electric_charge.h>
-#include <units/physical/si/energy.h>
-#include <units/physical/si/frequency.h>
-#include <units/physical/si/power.h>
-#include <units/physical/si/speed.h>
+#include <units/isq/si/amount_of_substance.h>
+#include <units/isq/si/thermodynamic_temperature.h>
+#include <units/isq/si/electric_charge.h>
+#include <units/isq/si/energy.h>
+#include <units/isq/si/frequency.h>
+#include <units/isq/si/power.h>
+#include <units/isq/si/speed.h>
 
-namespace units::physical::si::si2019 {
+namespace units::isq::si::si2019 {
 
 template<QuantityValue Rep = double>
 inline constexpr auto planck_constant = energy<joule, Rep>(6.62607015e-34) * time<second, Rep>(1);
@@ -59,4 +59,4 @@ inline constexpr auto hyperfine_structure_transition_frequency = frequency<hertz
 template<QuantityValue Rep = double>
 inline constexpr auto standard_gravity = acceleration<metre_per_second_sq, Rep>(9.80665);
 
-}  // namespace units::physical::si::si2019
+}  // namespace units::isq::si::si2019
diff --git a/src/include/units/physical/si/current_density.h b/src/include/units/isq/si/current_density.h
similarity index 81%
rename from src/include/units/physical/si/current_density.h
rename to src/include/units/isq/si/current_density.h
index 681977db..ff3630bc 100644
--- a/src/include/units/physical/si/current_density.h
+++ b/src/include/units/isq/si/current_density.h
@@ -22,17 +22,17 @@
 
 #pragma once
 
-#include <units/physical/dimensions/current_density.h>
-#include <units/physical/si/electric_current.h>
-#include <units/physical/si/length.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/current_density.h>
+#include <units/isq/si/electric_current.h>
+#include <units/isq/si/length.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct ampere_per_metre_sq : unit<ampere_per_metre_sq> {};
 
-struct dim_current_density : physical::dim_current_density<dim_current_density, ampere_per_metre_sq, dim_electric_current, dim_length> {};
+struct dim_current_density : isq::dim_current_density<dim_current_density, ampere_per_metre_sq, dim_electric_current, dim_length> {};
 
 template<UnitOf<dim_current_density> U, QuantityValue Rep = double>
 using current_density = quantity<dim_current_density, U, Rep>;
@@ -45,4 +45,4 @@ constexpr auto operator"" _q_A_per_m2(long double l) { return current_density<am
 
 }  // namespace literals
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/density.h b/src/include/units/isq/si/density.h
similarity index 83%
rename from src/include/units/physical/si/density.h
rename to src/include/units/isq/si/density.h
index b2e48998..cd691af4 100644
--- a/src/include/units/physical/si/density.h
+++ b/src/include/units/isq/si/density.h
@@ -22,17 +22,17 @@
 
 #pragma once
 
-#include <units/physical/dimensions/density.h>
-#include <units/physical/si/mass.h>
-#include <units/physical/si/length.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/density.h>
+#include <units/isq/si/mass.h>
+#include <units/isq/si/length.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct kilogram_per_metre_cub : unit<kilogram_per_metre_cub> {};
 
-struct dim_density : physical::dim_density<dim_density, kilogram_per_metre_cub, dim_mass, dim_length> {};
+struct dim_density : isq::dim_density<dim_density, kilogram_per_metre_cub, dim_mass, dim_length> {};
 
 template<UnitOf<dim_density> U, QuantityValue Rep = double>
 using density = quantity<dim_density, U, Rep>;
@@ -45,4 +45,4 @@ constexpr auto operator"" _q_kg_per_m3(long double l) { return density<kilogram_
 
 }  // namespace literals
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/dynamic_viscosity.h b/src/include/units/isq/si/dynamic_viscosity.h
similarity index 85%
rename from src/include/units/physical/si/dynamic_viscosity.h
rename to src/include/units/isq/si/dynamic_viscosity.h
index d3ee8531..0a9c2044 100644
--- a/src/include/units/physical/si/dynamic_viscosity.h
+++ b/src/include/units/isq/si/dynamic_viscosity.h
@@ -22,15 +22,15 @@
 
 #pragma once
 
-#include <units/physical/dimensions/dynamic_viscosity.h>
-#include <units/physical/si/time.h>
-#include <units/physical/si/pressure.h>
+#include <units/isq/dimensions/dynamic_viscosity.h>
+#include <units/isq/si/time.h>
+#include <units/isq/si/pressure.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct pascal_second : unit<pascal_second> {};
-struct dim_dynamic_viscosity : physical::dim_dynamic_viscosity<dim_dynamic_viscosity, pascal_second, dim_pressure, dim_time> {};
+struct dim_dynamic_viscosity : isq::dim_dynamic_viscosity<dim_dynamic_viscosity, pascal_second, dim_pressure, dim_time> {};
 
 template<UnitOf<dim_dynamic_viscosity> U, QuantityValue Rep = double>
 using dynamic_viscosity = quantity<dim_dynamic_viscosity, U, Rep>;
@@ -49,5 +49,5 @@ inline constexpr auto Pa_s = dynamic_viscosity<pascal_second, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
 
diff --git a/src/include/units/physical/si/electric_charge.h b/src/include/units/isq/si/electric_charge.h
similarity index 84%
rename from src/include/units/physical/si/electric_charge.h
rename to src/include/units/isq/si/electric_charge.h
index 0453f8ae..4c34f9b6 100644
--- a/src/include/units/physical/si/electric_charge.h
+++ b/src/include/units/isq/si/electric_charge.h
@@ -22,16 +22,16 @@
 
 #pragma once
 
-#include <units/physical/dimensions/electric_charge.h>
-#include <units/physical/si/electric_current.h>
-#include <units/physical/si/time.h>
+#include <units/isq/dimensions/electric_charge.h>
+#include <units/isq/si/electric_current.h>
+#include <units/isq/si/time.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct coulomb : named_unit<coulomb, "C", prefix> {};
 
-struct dim_electric_charge : physical::dim_electric_charge<dim_electric_charge, coulomb, dim_time, dim_electric_current> {};
+struct dim_electric_charge : isq::dim_electric_charge<dim_electric_charge, coulomb, dim_time, dim_electric_current> {};
 
 template<UnitOf<dim_electric_charge> U, QuantityValue Rep = double>
 using electric_charge = quantity<dim_electric_charge, U, Rep>;
@@ -50,4 +50,4 @@ inline constexpr auto C = electric_charge<coulomb, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/electric_current.h b/src/include/units/isq/si/electric_current.h
similarity index 97%
rename from src/include/units/physical/si/electric_current.h
rename to src/include/units/isq/si/electric_current.h
index a04d0a7c..a02e6381 100644
--- a/src/include/units/physical/si/electric_current.h
+++ b/src/include/units/isq/si/electric_current.h
@@ -23,11 +23,11 @@
 #pragma once
 
 #include <units/one_rep.h>
-#include <units/physical/dimensions/electric_current.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/electric_current.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct ampere : named_unit<ampere, "A", prefix> {};
 struct yoctoampere : prefixed_unit<yoctoampere, yocto, ampere> {};
@@ -51,7 +51,7 @@ struct exaampere : prefixed_unit<exaampere, exa, ampere> {};
 struct zettaampere : prefixed_unit<zettaampere, zetta, ampere> {};
 struct yottaampere : prefixed_unit<yottaampere, yotta, ampere> {};
 
-struct dim_electric_current : physical::dim_electric_current<ampere> {};
+struct dim_electric_current : isq::dim_electric_current<ampere> {};
 
 template<UnitOf<dim_electric_current> U, QuantityValue Rep = double>
 using electric_current = quantity<dim_electric_current, U, Rep>;
@@ -170,4 +170,4 @@ inline constexpr auto YA = electric_current<yottaampere, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/electric_field_strength.h b/src/include/units/isq/si/electric_field_strength.h
similarity index 84%
rename from src/include/units/physical/si/electric_field_strength.h
rename to src/include/units/isq/si/electric_field_strength.h
index 72e01aa9..b7155512 100644
--- a/src/include/units/physical/si/electric_field_strength.h
+++ b/src/include/units/isq/si/electric_field_strength.h
@@ -22,14 +22,14 @@
 
 #pragma once
 
-#include <units/physical/dimensions/electric_field_strength.h>
-#include <units/physical/si/voltage.h>
+#include <units/isq/dimensions/electric_field_strength.h>
+#include <units/isq/si/voltage.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct volt_per_metre : unit<volt_per_metre> {};
-struct dim_electric_field_strength : physical::dim_electric_field_strength<dim_electric_field_strength, volt_per_metre, dim_voltage, dim_length> {};
+struct dim_electric_field_strength : isq::dim_electric_field_strength<dim_electric_field_strength, volt_per_metre, dim_voltage, dim_length> {};
 
 template<UnitOf<dim_electric_field_strength> U, QuantityValue Rep = double>
 using electric_field_strength = quantity<dim_electric_field_strength, U, Rep>;
@@ -42,4 +42,4 @@ constexpr auto operator"" _q_V_per_m(long double l) { return electric_field_stre
 
 }  // namespace literals
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/energy.h b/src/include/units/isq/si/energy.h
similarity index 97%
rename from src/include/units/physical/si/energy.h
rename to src/include/units/isq/si/energy.h
index 3410bef4..a412d40e 100644
--- a/src/include/units/physical/si/energy.h
+++ b/src/include/units/isq/si/energy.h
@@ -22,12 +22,12 @@
 
 #pragma once
 
-#include <units/physical/dimensions/energy.h>
-#include <units/physical/si/force.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/energy.h>
+#include <units/isq/si/force.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct joule : named_unit<joule, "J", prefix> {};
 struct yoctojoule : prefixed_unit<yoctojoule, yocto, joule> {};
@@ -50,7 +50,7 @@ struct yottajoule : prefixed_unit<yottajoule, yotta, joule> {};
 struct electronvolt : named_scaled_unit<electronvolt, "eV", prefix, ratio(1'602'176'634, 1'000'000'000, -19), joule> {};
 struct gigaelectronvolt : prefixed_unit<gigaelectronvolt, giga, electronvolt> {};
 
-struct dim_energy : physical::dim_energy<dim_energy, joule, dim_force, dim_length> {};
+struct dim_energy : isq::dim_energy<dim_energy, joule, dim_force, dim_length> {};
 
 template<UnitOf<dim_energy> U, QuantityValue Rep = double>
 using energy = quantity<dim_energy, U, Rep>;
@@ -159,4 +159,4 @@ inline constexpr auto GeV = energy<gigaelectronvolt, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/energy_density.h b/src/include/units/isq/si/energy_density.h
similarity index 84%
rename from src/include/units/physical/si/energy_density.h
rename to src/include/units/isq/si/energy_density.h
index 881acf3a..9458680f 100644
--- a/src/include/units/physical/si/energy_density.h
+++ b/src/include/units/isq/si/energy_density.h
@@ -22,15 +22,15 @@
 
 #pragma once
 
-#include <units/physical/dimensions/energy_density.h>
-#include <units/physical/si/energy.h>
-#include <units/physical/si/volume.h>
+#include <units/isq/dimensions/energy_density.h>
+#include <units/isq/si/energy.h>
+#include <units/isq/si/volume.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct joule_per_metre_cub : unit<joule_per_metre_cub> {};
-struct dim_energy_density : physical::dim_energy_density<dim_energy_density, joule_per_metre_cub, dim_energy, dim_volume> {};
+struct dim_energy_density : isq::dim_energy_density<dim_energy_density, joule_per_metre_cub, dim_energy, dim_volume> {};
 
 template<UnitOf<dim_energy_density> U, QuantityValue Rep = double>
 using energy_density = quantity<dim_energy_density, U, Rep>;
@@ -43,4 +43,4 @@ constexpr auto operator"" _q_J_per_m3(long double l) { return energy_density<jou
 
 }  // namespace literals
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/force.h b/src/include/units/isq/si/force.h
similarity index 96%
rename from src/include/units/physical/si/force.h
rename to src/include/units/isq/si/force.h
index cf51ad72..168ba049 100644
--- a/src/include/units/physical/si/force.h
+++ b/src/include/units/isq/si/force.h
@@ -22,13 +22,13 @@
 
 #pragma once
 
-#include <units/physical/dimensions/force.h>
-#include <units/physical/si/acceleration.h>
-#include <units/physical/si/mass.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/force.h>
+#include <units/isq/si/acceleration.h>
+#include <units/isq/si/mass.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct newton : named_unit<newton, "N", prefix> {};
 struct yoctonewton : prefixed_unit<yoctonewton, yocto, newton> {};
@@ -52,7 +52,7 @@ struct exanewton : prefixed_unit<exanewton, exa, newton> {};
 struct zettanewton : prefixed_unit<zettanewton, zetta, newton> {};
 struct yottanewton : prefixed_unit<yottanewton, yotta, newton> {};
 
-struct dim_force : physical::dim_force<dim_force, newton, dim_mass, dim_acceleration> {};
+struct dim_force : isq::dim_force<dim_force, newton, dim_mass, dim_acceleration> {};
 
 template<UnitOf<dim_force> U, QuantityValue Rep = double>
 using force = quantity<dim_force, U, Rep>;
@@ -171,4 +171,4 @@ inline constexpr auto YN = force<yottanewton, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/fps/acceleration.h b/src/include/units/isq/si/fps/acceleration.h
similarity index 85%
rename from src/include/units/physical/si/fps/acceleration.h
rename to src/include/units/isq/si/fps/acceleration.h
index 1a03e622..dd0c7fc4 100644
--- a/src/include/units/physical/si/fps/acceleration.h
+++ b/src/include/units/isq/si/fps/acceleration.h
@@ -22,14 +22,14 @@
 
 #pragma once
 
-#include <units/physical/dimensions/acceleration.h>
-#include <units/physical/si/fps/speed.h>
+#include <units/isq/dimensions/acceleration.h>
+#include <units/isq/si/fps/speed.h>
 #include <units/quantity.h>
 
-namespace units::physical::si::fps {
+namespace units::isq::si::fps {
 
 struct foot_per_second_sq : unit<foot_per_second_sq> {};
-struct dim_acceleration : physical::dim_acceleration<dim_acceleration, foot_per_second_sq, dim_length, dim_time> {};
+struct dim_acceleration : isq::dim_acceleration<dim_acceleration, foot_per_second_sq, dim_length, dim_time> {};
 
 template<UnitOf<dim_acceleration> U, QuantityValue Rep = double>
 using acceleration = quantity<dim_acceleration, U, Rep>;
@@ -42,4 +42,4 @@ constexpr auto operator"" _q_ft_per_s2(long double l) { return acceleration<foot
 
 }  // namespace literals
 
-}  // namespace units::physical::si::fps
+}  // namespace units::isq::si::fps
diff --git a/src/include/units/physical/si/fps/area.h b/src/include/units/isq/si/fps/area.h
similarity index 88%
rename from src/include/units/physical/si/fps/area.h
rename to src/include/units/isq/si/fps/area.h
index a9703f20..34a75283 100644
--- a/src/include/units/physical/si/fps/area.h
+++ b/src/include/units/isq/si/fps/area.h
@@ -22,14 +22,14 @@
 
 #pragma once
 
-#include <units/physical/dimensions/area.h>
-#include <units/physical/si/fps/length.h>
+#include <units/isq/dimensions/area.h>
+#include <units/isq/si/fps/length.h>
 #include <units/quantity.h>
 
-namespace units::physical::si::fps {
+namespace units::isq::si::fps {
 
 struct square_foot : unit<square_foot> {};
-struct dim_area : physical::dim_area<dim_area, square_foot, dim_length> {};
+struct dim_area : isq::dim_area<dim_area, square_foot, dim_length> {};
 
 
 template<UnitOf<dim_area> U, QuantityValue Rep = double>
@@ -49,4 +49,4 @@ inline constexpr auto ft2 = area<square_foot, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::fps
+}  // namespace units::isq::si::fps
diff --git a/src/include/units/physical/si/fps/density.h b/src/include/units/isq/si/fps/density.h
similarity index 84%
rename from src/include/units/physical/si/fps/density.h
rename to src/include/units/isq/si/fps/density.h
index dab3d912..82a1742e 100644
--- a/src/include/units/physical/si/fps/density.h
+++ b/src/include/units/isq/si/fps/density.h
@@ -22,16 +22,16 @@
 
 #pragma once
 
-#include <units/physical/dimensions/density.h>
-#include <units/physical/si/fps/mass.h>
-#include <units/physical/si/fps/length.h>
+#include <units/isq/dimensions/density.h>
+#include <units/isq/si/fps/mass.h>
+#include <units/isq/si/fps/length.h>
 #include <units/quantity.h>
 
-namespace units::physical::si::fps {
+namespace units::isq::si::fps {
 
 struct pound_per_foot_cub : unit<pound_per_foot_cub> {};
 
-struct dim_density : physical::dim_density<dim_density, pound_per_foot_cub, dim_mass, dim_length> {};
+struct dim_density : isq::dim_density<dim_density, pound_per_foot_cub, dim_mass, dim_length> {};
 
 template<UnitOf<dim_density> U, QuantityValue Rep = double>
 using density = quantity<dim_density, U, Rep>;
@@ -44,4 +44,4 @@ constexpr auto operator"" _q_lb_per_ft3(long double l) { return density<pound_pe
 
 }  // namespace literals
 
-}  // namespace units::physical::si::fps
+}  // namespace units::isq::si::fps
diff --git a/src/include/units/physical/si/fps/energy.h b/src/include/units/isq/si/fps/energy.h
similarity index 88%
rename from src/include/units/physical/si/fps/energy.h
rename to src/include/units/isq/si/fps/energy.h
index 9eb6d0ce..d1a406b0 100644
--- a/src/include/units/physical/si/fps/energy.h
+++ b/src/include/units/isq/si/fps/energy.h
@@ -22,17 +22,17 @@
 
 #pragma once
 
-#include <units/physical/dimensions/energy.h>
-#include <units/physical/si/fps/force.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/energy.h>
+#include <units/isq/si/fps/force.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si::fps {
+namespace units::isq::si::fps {
 
 // https://en.wikipedia.org/wiki/Foot-poundal
 struct foot_poundal : unit<foot_poundal> {};
 
-struct dim_energy : physical::dim_energy<dim_energy, foot_poundal, dim_force, dim_length> {};
+struct dim_energy : isq::dim_energy<dim_energy, foot_poundal, dim_force, dim_length> {};
 
 // https://en.wikipedia.org/wiki/Foot-pound_(energy)
 struct foot_pound_force : noble_deduced_unit<foot_pound_force, dim_energy, pound_force, foot> {};
@@ -62,4 +62,4 @@ inline constexpr auto ft_lbf = energy<foot_pound_force, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::fps
+}  // namespace units::isq::si::fps
diff --git a/src/include/units/physical/si/fps/force.h b/src/include/units/isq/si/fps/force.h
similarity index 89%
rename from src/include/units/physical/si/fps/force.h
rename to src/include/units/isq/si/fps/force.h
index cc53c2fe..cf2cb87b 100644
--- a/src/include/units/physical/si/fps/force.h
+++ b/src/include/units/isq/si/fps/force.h
@@ -22,13 +22,13 @@
 
 #pragma once
 
-#include <units/physical/dimensions/force.h>
-#include <units/physical/si/fps/acceleration.h>
-#include <units/physical/si/fps/mass.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/force.h>
+#include <units/isq/si/fps/acceleration.h>
+#include <units/isq/si/fps/mass.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si::fps {
+namespace units::isq::si::fps {
 
 // https://en.wikipedia.org/wiki/Poundal
 struct poundal : named_unit<poundal, "pdl", no_prefix> {};
@@ -41,7 +41,7 @@ struct kilopound_force : prefixed_unit<kilopound_force, si::kilo, pound_force> {
 // https://en.wikipedia.org/wiki/Kip_(unit), 
 struct kip : alias_unit<kilopound_force, "klbf", no_prefix> {};
 
-struct dim_force : physical::dim_force<dim_force, poundal, dim_mass, dim_acceleration> {};
+struct dim_force : isq::dim_force<dim_force, poundal, dim_mass, dim_acceleration> {};
 
 template<UnitOf<dim_force> U, QuantityValue Rep = double>
 using force = quantity<dim_force, U, Rep>;
@@ -70,4 +70,4 @@ inline constexpr auto klbf = force<kilopound_force, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::fps
+}  // namespace units::isq::si::fps
diff --git a/src/include/units/isq/si/fps/fps.h b/src/include/units/isq/si/fps/fps.h
new file mode 100644
index 00000000..c71f5c45
--- /dev/null
+++ b/src/include/units/isq/si/fps/fps.h
@@ -0,0 +1,37 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2018 Mateusz Pusz
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#pragma once
+
+#include <units/isq/si/fps/length.h>
+#include <units/isq/si/fps/mass.h>
+#include <units/isq/si/fps/time.h>
+
+#include <units/isq/si/fps/acceleration.h>
+#include <units/isq/si/fps/area.h>
+#include <units/isq/si/fps/density.h>
+#include <units/isq/si/fps/energy.h>
+#include <units/isq/si/fps/force.h>
+#include <units/isq/si/fps/power.h>
+#include <units/isq/si/fps/pressure.h>
+#include <units/isq/si/fps/speed.h>
+#include <units/isq/si/fps/volume.h>
diff --git a/src/include/units/physical/si/fps/length.h b/src/include/units/isq/si/fps/length.h
similarity index 96%
rename from src/include/units/physical/si/fps/length.h
rename to src/include/units/isq/si/fps/length.h
index 311ab368..3aa57dd3 100644
--- a/src/include/units/physical/si/fps/length.h
+++ b/src/include/units/isq/si/fps/length.h
@@ -22,10 +22,10 @@
 
 #pragma once
 
-#include <units/physical/si/length.h>
+#include <units/isq/si/length.h>
 #include <units/quantity.h>
 
-namespace units::physical::si::fps {
+namespace units::isq::si::fps {
 
 // https://en.wikipedia.org/wiki/Foot_(unit)
 struct foot : named_scaled_unit<foot, "ft", no_prefix, ratio(3'048, 1'000, -1), si::metre> {};
@@ -49,7 +49,7 @@ struct nautical_mile : named_scaled_unit<nautical_mile, "mi(naut)", no_prefix, r
 
 
 
-struct dim_length : physical::dim_length<foot> {};
+struct dim_length : isq::dim_length<foot> {};
 
 template<UnitOf<dim_length> U, QuantityValue Rep = double>
 using length = quantity<dim_length, U, Rep>;
@@ -108,4 +108,4 @@ inline constexpr auto naut_mi = length<nautical_mile, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::fps
+}  // namespace units::isq::si::fps
diff --git a/src/include/units/physical/si/fps/mass.h b/src/include/units/isq/si/fps/mass.h
similarity index 96%
rename from src/include/units/physical/si/fps/mass.h
rename to src/include/units/isq/si/fps/mass.h
index ecb405df..a2b9814e 100644
--- a/src/include/units/physical/si/fps/mass.h
+++ b/src/include/units/isq/si/fps/mass.h
@@ -22,15 +22,15 @@
 
 #pragma once
 
-#include <units/physical/si/mass.h>
+#include <units/isq/si/mass.h>
 #include <units/quantity.h>
 
-namespace units::physical::si::fps {
+namespace units::isq::si::fps {
 
 // https://en.wikipedia.org/wiki/Pound_(mass)
 struct pound : named_scaled_unit<pound, "lb", no_prefix, ratio(45'359'237, 100'000'000), si::kilogram> {};
 
-struct dim_mass : physical::dim_mass<pound> {};
+struct dim_mass : isq::dim_mass<pound> {};
 
 template<UnitOf<dim_mass> U, QuantityValue Rep = double>
 using mass = quantity<dim_mass, U, Rep>;
@@ -105,4 +105,4 @@ inline constexpr auto lton = mass<long_ton, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::fps
+}  // namespace units::isq::si::fps
diff --git a/src/include/units/physical/si/fps/power.h b/src/include/units/isq/si/fps/power.h
similarity index 90%
rename from src/include/units/physical/si/fps/power.h
rename to src/include/units/isq/si/fps/power.h
index cf7ded79..3dee4ca6 100644
--- a/src/include/units/physical/si/fps/power.h
+++ b/src/include/units/isq/si/fps/power.h
@@ -22,16 +22,16 @@
 
 #pragma once
 
-#include <units/physical/dimensions/power.h>
-#include <units/physical/si/fps/energy.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/power.h>
+#include <units/isq/si/fps/energy.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si::fps {
+namespace units::isq::si::fps {
 
 struct foot_poundal_per_second : unit<foot_poundal_per_second> {};
 
-struct dim_power : physical::dim_power<dim_power, foot_poundal_per_second, dim_energy, dim_time> {};
+struct dim_power : isq::dim_power<dim_power, foot_poundal_per_second, dim_energy, dim_time> {};
 
 struct foot_pound_force_per_second : deduced_unit<foot_pound_force_per_second, dim_power, foot_pound_force, second> {};
 
@@ -62,4 +62,4 @@ inline constexpr auto hp = power<horse_power, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::fps
+}  // namespace units::isq::si::fps
diff --git a/src/include/units/physical/si/fps/pressure.h b/src/include/units/isq/si/fps/pressure.h
similarity index 89%
rename from src/include/units/physical/si/fps/pressure.h
rename to src/include/units/isq/si/fps/pressure.h
index 52a3997f..d3821785 100644
--- a/src/include/units/physical/si/fps/pressure.h
+++ b/src/include/units/isq/si/fps/pressure.h
@@ -22,17 +22,17 @@
 
 #pragma once
 
-#include <units/physical/dimensions/pressure.h>
-#include <units/physical/si/fps/area.h>
-#include <units/physical/si/fps/force.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/pressure.h>
+#include <units/isq/si/fps/area.h>
+#include <units/isq/si/fps/force.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si::fps {
+namespace units::isq::si::fps {
 
 struct poundal_per_foot_sq : unit<poundal_per_foot_sq> {};
 
-struct dim_pressure : physical::dim_pressure<dim_pressure, poundal_per_foot_sq, dim_force, dim_area> {};
+struct dim_pressure : isq::dim_pressure<dim_pressure, poundal_per_foot_sq, dim_force, dim_area> {};
 
 template<UnitOf<dim_pressure> U, QuantityValue Rep = double>
 using pressure = quantity<dim_pressure, U, Rep>;
@@ -66,4 +66,4 @@ inline constexpr auto kpsi = pressure<kilopound_force_per_inch_sq, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::fps
+}  // namespace units::isq::si::fps
diff --git a/src/include/units/physical/si/fps/speed.h b/src/include/units/isq/si/fps/speed.h
similarity index 90%
rename from src/include/units/physical/si/fps/speed.h
rename to src/include/units/isq/si/fps/speed.h
index 6763b303..d576aa0c 100644
--- a/src/include/units/physical/si/fps/speed.h
+++ b/src/include/units/isq/si/fps/speed.h
@@ -22,15 +22,15 @@
 
 #pragma once
 
-#include <units/physical/dimensions/speed.h>
-#include <units/physical/si/fps/length.h>
-#include <units/physical/si/fps/time.h>
+#include <units/isq/dimensions/speed.h>
+#include <units/isq/si/fps/length.h>
+#include <units/isq/si/fps/time.h>
 #include <units/quantity.h>
 
-namespace units::physical::si::fps {
+namespace units::isq::si::fps {
 
 struct foot_per_second : unit<foot_per_second> {};
-struct dim_speed : physical::dim_speed<dim_speed, foot_per_second, dim_length, dim_time> {};
+struct dim_speed : isq::dim_speed<dim_speed, foot_per_second, dim_length, dim_time> {};
 
 template<UnitOf<dim_speed> U, QuantityValue Rep = double>
 using speed = quantity<dim_speed, U, Rep>;
@@ -65,4 +65,4 @@ inline constexpr auto knot = speed<fps::knot, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::fps
+}  // namespace units::isq::si::fps
diff --git a/src/include/units/physical/si/fps/time.h b/src/include/units/isq/si/fps/time.h
similarity index 92%
rename from src/include/units/physical/si/fps/time.h
rename to src/include/units/isq/si/fps/time.h
index d156ed70..90738c4a 100644
--- a/src/include/units/physical/si/fps/time.h
+++ b/src/include/units/isq/si/fps/time.h
@@ -22,10 +22,10 @@
 
 #pragma once
 
-#include <units/physical/si/time.h>
+#include <units/isq/si/time.h>
 #include <units/quantity.h>
 
-namespace units::physical::si::fps {
+namespace units::isq::si::fps {
 
 using si::second;
 using si::minute;
@@ -46,4 +46,4 @@ using si::unit_constants::s;
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::fps
+}  // namespace units::isq::si::fps
diff --git a/src/include/units/physical/si/fps/volume.h b/src/include/units/isq/si/fps/volume.h
similarity index 89%
rename from src/include/units/physical/si/fps/volume.h
rename to src/include/units/isq/si/fps/volume.h
index 7b4f0396..c1d8baf3 100644
--- a/src/include/units/physical/si/fps/volume.h
+++ b/src/include/units/isq/si/fps/volume.h
@@ -22,14 +22,14 @@
 
 #pragma once
 
-#include <units/physical/dimensions/volume.h>
-#include <units/physical/si/fps/length.h>
+#include <units/isq/dimensions/volume.h>
+#include <units/isq/si/fps/length.h>
 #include <units/quantity.h>
 
-namespace units::physical::si::fps {
+namespace units::isq::si::fps {
 
 struct cubic_foot : unit<cubic_foot> {};
-struct dim_volume : physical::dim_volume<dim_volume, cubic_foot, dim_length> {};
+struct dim_volume : isq::dim_volume<dim_volume, cubic_foot, dim_length> {};
 
 struct cubic_yard : deduced_unit<cubic_yard, dim_volume, yard> {};
 
@@ -55,4 +55,4 @@ inline constexpr auto yd3 = volume<cubic_yard, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::fps
+}  // namespace units::isq::si::fps
diff --git a/src/include/units/physical/si/frequency.h b/src/include/units/isq/si/frequency.h
similarity index 97%
rename from src/include/units/physical/si/frequency.h
rename to src/include/units/isq/si/frequency.h
index 21a8daa3..871f1eed 100644
--- a/src/include/units/physical/si/frequency.h
+++ b/src/include/units/isq/si/frequency.h
@@ -22,11 +22,11 @@
 
 #pragma once
 
-#include <units/physical/dimensions/frequency.h>
-#include <units/physical/si/time.h>
+#include <units/isq/dimensions/frequency.h>
+#include <units/isq/si/time.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct hertz : named_unit<hertz, "Hz", prefix> {};
 struct yoctohertz : prefixed_unit<yoctohertz, yocto, hertz> {};
@@ -46,7 +46,7 @@ struct exahertz : prefixed_unit<exahertz, exa, hertz> {};
 struct zettahertz : prefixed_unit<zettahertz, zetta, hertz> {};
 struct yottahertz : prefixed_unit<yottahertz, yotta, hertz> {};
 
-struct dim_frequency : physical::dim_frequency<dim_frequency, hertz, dim_time> {};
+struct dim_frequency : isq::dim_frequency<dim_frequency, hertz, dim_time> {};
 
 template<UnitOf<dim_frequency> U, QuantityValue Rep = double>
 using frequency = quantity<dim_frequency, U, Rep>;
@@ -145,4 +145,4 @@ inline constexpr auto YHz = frequency<yottahertz, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/heat_capacity.h b/src/include/units/isq/si/heat_capacity.h
similarity index 79%
rename from src/include/units/physical/si/heat_capacity.h
rename to src/include/units/isq/si/heat_capacity.h
index a4f2f2d2..49a1300a 100644
--- a/src/include/units/physical/si/heat_capacity.h
+++ b/src/include/units/isq/si/heat_capacity.h
@@ -22,22 +22,22 @@
 
 #pragma once
 
-#include <units/physical/dimensions/heat_capacity.h>
-#include <units/physical/si/thermodynamic_temperature.h>
-#include <units/physical/si/energy.h>
-#include <units/physical/si/mass.h>
-#include <units/physical/si/amount_of_substance.h>
+#include <units/isq/dimensions/heat_capacity.h>
+#include <units/isq/si/thermodynamic_temperature.h>
+#include <units/isq/si/energy.h>
+#include <units/isq/si/mass.h>
+#include <units/isq/si/amount_of_substance.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct joule_per_kelvin : unit<joule_per_kelvin> {};
 struct joule_per_kilogram_kelvin : unit<joule_per_kilogram_kelvin> {};
 struct joule_per_mole_kelvin : unit<joule_per_mole_kelvin> {};
 
-struct dim_heat_capacity : physical::dim_heat_capacity<dim_heat_capacity, joule_per_kelvin, dim_energy, dim_thermodynamic_temperature> {};
-struct dim_specific_heat_capacity : physical::dim_specific_heat_capacity<dim_specific_heat_capacity, joule_per_kilogram_kelvin, dim_heat_capacity, dim_mass> {};
-struct dim_molar_heat_capacity : physical::dim_molar_heat_capacity<dim_molar_heat_capacity, joule_per_mole_kelvin, dim_heat_capacity, dim_amount_of_substance> {};
+struct dim_heat_capacity : isq::dim_heat_capacity<dim_heat_capacity, joule_per_kelvin, dim_energy, dim_thermodynamic_temperature> {};
+struct dim_specific_heat_capacity : isq::dim_specific_heat_capacity<dim_specific_heat_capacity, joule_per_kilogram_kelvin, dim_heat_capacity, dim_mass> {};
+struct dim_molar_heat_capacity : isq::dim_molar_heat_capacity<dim_molar_heat_capacity, joule_per_mole_kelvin, dim_heat_capacity, dim_amount_of_substance> {};
 
 template<UnitOf<dim_heat_capacity> U, QuantityValue Rep = double>
 using heat_capacity = quantity<dim_heat_capacity, U, Rep>;
@@ -64,5 +64,5 @@ constexpr auto operator"" _q_J_per_mol_K(long double l) { return molar_heat_capa
 
 }  // namespace literals
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
 
diff --git a/src/include/units/physical/si/iau/iau.h b/src/include/units/isq/si/iau/iau.h
similarity index 96%
rename from src/include/units/physical/si/iau/iau.h
rename to src/include/units/isq/si/iau/iau.h
index dcaf7e1d..6fc641ce 100644
--- a/src/include/units/physical/si/iau/iau.h
+++ b/src/include/units/isq/si/iau/iau.h
@@ -22,4 +22,4 @@
 
 #pragma once
 
-#include <units/physical/si/iau/length.h>
+#include <units/isq/si/iau/length.h>
diff --git a/src/include/units/physical/si/iau/length.h b/src/include/units/isq/si/iau/length.h
similarity index 95%
rename from src/include/units/physical/si/iau/length.h
rename to src/include/units/isq/si/iau/length.h
index 27e558dd..cfc6974f 100644
--- a/src/include/units/physical/si/iau/length.h
+++ b/src/include/units/isq/si/iau/length.h
@@ -23,9 +23,9 @@
 
 #pragma once
 
-#include <units/physical/si/length.h>
+#include <units/isq/si/length.h>
 
-namespace units::physical::si::iau {
+namespace units::isq::si::iau {
 
 // https://en.wikipedia.org/wiki/Light-year
 struct light_year : named_scaled_unit<light_year, "ly", no_prefix, ratio(9460730472580800), si::metre> {};
@@ -60,4 +60,4 @@ inline constexpr auto angstrom = si::length<iau::angstrom, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::iau
+}  // namespace units::isq::si::iau
diff --git a/src/include/units/physical/si/imperial/imperial.h b/src/include/units/isq/si/imperial/imperial.h
similarity index 96%
rename from src/include/units/physical/si/imperial/imperial.h
rename to src/include/units/isq/si/imperial/imperial.h
index ab19db50..1031971e 100644
--- a/src/include/units/physical/si/imperial/imperial.h
+++ b/src/include/units/isq/si/imperial/imperial.h
@@ -22,4 +22,4 @@
 
 #pragma once
 
-#include <units/physical/si/imperial/length.h>
+#include <units/isq/si/imperial/length.h>
diff --git a/src/include/units/physical/si/imperial/length.h b/src/include/units/isq/si/imperial/length.h
similarity index 94%
rename from src/include/units/physical/si/imperial/length.h
rename to src/include/units/isq/si/imperial/length.h
index e632b8f9..0697af2b 100644
--- a/src/include/units/physical/si/imperial/length.h
+++ b/src/include/units/isq/si/imperial/length.h
@@ -22,9 +22,9 @@
 
 #pragma once
 
-#include <units/physical/si/international/length.h>
+#include <units/isq/si/international/length.h>
 
-namespace units::physical::si::imperial {
+namespace units::isq::si::imperial {
 
 // https://en.wikipedia.org/wiki/Chain_(unit)
 struct chain : named_scaled_unit<chain, "ch", no_prefix, ratio(22, 1), si::international::yard> {};
@@ -51,4 +51,4 @@ inline constexpr auto rd = si::length<rod, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::imperial
+}  // namespace units::isq::si::imperial
diff --git a/src/include/units/physical/si/inductance.h b/src/include/units/isq/si/inductance.h
similarity index 96%
rename from src/include/units/physical/si/inductance.h
rename to src/include/units/isq/si/inductance.h
index 42e7460d..84af4a6f 100644
--- a/src/include/units/physical/si/inductance.h
+++ b/src/include/units/isq/si/inductance.h
@@ -22,12 +22,12 @@
 
 #pragma once
 
-#include <units/physical/dimensions/inductance.h>
-#include <units/physical/si/magnetic_flux.h>
-#include <units/physical/si/electric_current.h>
+#include <units/isq/dimensions/inductance.h>
+#include <units/isq/si/magnetic_flux.h>
+#include <units/isq/si/electric_current.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct henry : named_unit<henry, "H", prefix> {};
 
@@ -48,7 +48,7 @@ struct exahenry : prefixed_unit<exahenry, exa, henry> {};
 struct zettahenry : prefixed_unit<zettahenry, zetta, henry> {};
 struct yottahenry : prefixed_unit<yottahenry, yotta, henry> {};
 
-struct dim_inductance : physical::dim_inductance<dim_inductance, henry, dim_magnetic_flux, dim_electric_current> {};
+struct dim_inductance : isq::dim_inductance<dim_inductance, henry, dim_magnetic_flux, dim_electric_current> {};
 
 template<UnitOf<dim_inductance> U, QuantityValue Rep = double>
 using inductance = quantity<dim_inductance, U, Rep>;
@@ -147,4 +147,4 @@ inline constexpr auto YH = inductance<yottahenry, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/international/area.h b/src/include/units/isq/si/international/area.h
similarity index 90%
rename from src/include/units/physical/si/international/area.h
rename to src/include/units/isq/si/international/area.h
index d36b722d..90a7513b 100644
--- a/src/include/units/physical/si/international/area.h
+++ b/src/include/units/isq/si/international/area.h
@@ -22,10 +22,10 @@
 
 #pragma once
 
-#include <units/physical/si/area.h>
-#include <units/physical/si/international/length.h>
+#include <units/isq/si/area.h>
+#include <units/isq/si/international/length.h>
 
-namespace units::physical::si::international {
+namespace units::isq::si::international {
 
 struct square_foot : deduced_unit<square_foot, si::dim_area, si::international::foot> {};
 
@@ -43,4 +43,4 @@ inline constexpr auto ft2 = si::area<square_foot, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::international
+}  // namespace units::isq::si::international
diff --git a/src/include/units/physical/si/international/international.h b/src/include/units/isq/si/international/international.h
similarity index 84%
rename from src/include/units/physical/si/international/international.h
rename to src/include/units/isq/si/international/international.h
index 39ab95bc..4a2c1242 100644
--- a/src/include/units/physical/si/international/international.h
+++ b/src/include/units/isq/si/international/international.h
@@ -22,8 +22,8 @@
 
 #pragma once
 
-#include <units/physical/si/international/length.h>
+#include <units/isq/si/international/length.h>
 
-#include <units/physical/si/international/area.h>
-#include <units/physical/si/international/speed.h>
-#include <units/physical/si/international/volume.h>
+#include <units/isq/si/international/area.h>
+#include <units/isq/si/international/speed.h>
+#include <units/isq/si/international/volume.h>
diff --git a/src/include/units/physical/si/international/length.h b/src/include/units/isq/si/international/length.h
similarity index 97%
rename from src/include/units/physical/si/international/length.h
rename to src/include/units/isq/si/international/length.h
index 3d6f34b0..179278e1 100644
--- a/src/include/units/physical/si/international/length.h
+++ b/src/include/units/isq/si/international/length.h
@@ -23,9 +23,9 @@
 
 #pragma once
 
-#include <units/physical/si/length.h>
+#include <units/isq/si/length.h>
 
-namespace units::physical::si::international {
+namespace units::isq::si::international {
 
 // si::international yard
 // https://en.wikipedia.org/wiki/International_yard_and_pound
@@ -107,4 +107,4 @@ inline constexpr auto mil = si::length<international::mil, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::international
+}  // namespace units::isq::si::international
diff --git a/src/include/units/physical/si/international/speed.h b/src/include/units/isq/si/international/speed.h
similarity index 89%
rename from src/include/units/physical/si/international/speed.h
rename to src/include/units/isq/si/international/speed.h
index 70cc3f62..7be951b9 100644
--- a/src/include/units/physical/si/international/speed.h
+++ b/src/include/units/isq/si/international/speed.h
@@ -22,10 +22,10 @@
 
 #pragma once
 
-#include <units/physical/si/speed.h>
-#include <units/physical/si/international/length.h>
+#include <units/isq/si/speed.h>
+#include <units/isq/si/international/length.h>
 
-namespace units::physical::si::international {
+namespace units::isq::si::international {
 
 struct mile_per_hour : deduced_unit<mile_per_hour, si::dim_speed, si::international::mile, si::hour> {};
 
@@ -37,4 +37,4 @@ constexpr auto operator"" _q_mi_per_h(long double l) { return si::speed<mile_per
 
 }  // namespace literals
 
-}  // namespace units::physical::si::international
+}  // namespace units::isq::si::international
diff --git a/src/include/units/physical/si/international/volume.h b/src/include/units/isq/si/international/volume.h
similarity index 90%
rename from src/include/units/physical/si/international/volume.h
rename to src/include/units/isq/si/international/volume.h
index 11a43ae6..3901a757 100644
--- a/src/include/units/physical/si/international/volume.h
+++ b/src/include/units/isq/si/international/volume.h
@@ -22,10 +22,10 @@
 
 #pragma once
 
-#include <units/physical/si/volume.h>
-#include <units/physical/si/international/length.h>
+#include <units/isq/si/volume.h>
+#include <units/isq/si/international/length.h>
 
-namespace units::physical::si::international {
+namespace units::isq::si::international {
 
 struct cubic_foot : deduced_unit<cubic_foot, si::dim_volume, si::international::foot> {};
 
@@ -43,4 +43,4 @@ inline constexpr auto ft3 = si::volume<cubic_foot, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::international
+}  // namespace units::isq::si::international
diff --git a/src/include/units/physical/si/length.h b/src/include/units/isq/si/length.h
similarity index 98%
rename from src/include/units/physical/si/length.h
rename to src/include/units/isq/si/length.h
index 781bf795..4caa491e 100644
--- a/src/include/units/physical/si/length.h
+++ b/src/include/units/isq/si/length.h
@@ -23,11 +23,11 @@
 #pragma once
 
 #include <units/one_rep.h>
-#include <units/physical/dimensions/length.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/length.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct metre : named_unit<metre, "m", prefix> {};
 struct yoctometre : prefixed_unit<yoctometre, yocto, metre> {};
@@ -53,7 +53,7 @@ struct yottametre : prefixed_unit<yottametre, yotta, metre> {};
 
 struct astronomical_unit : named_scaled_unit<astronomical_unit, "au", no_prefix, ratio(149'597'870'700), metre> {};
 
-struct dim_length : physical::dim_length<metre> {};
+struct dim_length : isq::dim_length<metre> {};
 
 template<UnitOf<dim_length> U, QuantityValue Rep = double>
 using length = quantity<dim_length, U, Rep>;
@@ -177,4 +177,4 @@ inline constexpr auto au = length<astronomical_unit, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/luminance.h b/src/include/units/isq/si/luminance.h
similarity index 84%
rename from src/include/units/physical/si/luminance.h
rename to src/include/units/isq/si/luminance.h
index d094f166..edb47115 100644
--- a/src/include/units/physical/si/luminance.h
+++ b/src/include/units/isq/si/luminance.h
@@ -22,15 +22,15 @@
 
 #pragma once
 
-#include <units/physical/dimensions/luminance.h>
-#include <units/physical/si/length.h>
-#include <units/physical/si/luminous_intensity.h>
+#include <units/isq/dimensions/luminance.h>
+#include <units/isq/si/length.h>
+#include <units/isq/si/luminous_intensity.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct candela_per_metre_sq : unit<candela_per_metre_sq> {};
-struct dim_luminance : physical::dim_luminance<dim_luminance, candela_per_metre_sq, dim_luminous_intensity, dim_length> {};
+struct dim_luminance : isq::dim_luminance<dim_luminance, candela_per_metre_sq, dim_luminous_intensity, dim_length> {};
 
 template<UnitOf<dim_luminance> U, QuantityValue Rep = double>
 using luminance = quantity<dim_luminance, U, Rep>;
@@ -43,5 +43,5 @@ constexpr auto operator"" _q_cd_per_m2(long double l) { return luminance<candela
 
 }  // namespace literals
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
 
diff --git a/src/include/units/physical/si/luminous_intensity.h b/src/include/units/isq/si/luminous_intensity.h
similarity index 97%
rename from src/include/units/physical/si/luminous_intensity.h
rename to src/include/units/isq/si/luminous_intensity.h
index e39531fe..85989cd9 100644
--- a/src/include/units/physical/si/luminous_intensity.h
+++ b/src/include/units/isq/si/luminous_intensity.h
@@ -23,11 +23,11 @@
 #pragma once
 
 #include <units/one_rep.h>
-#include <units/physical/dimensions/luminous_intensity.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/luminous_intensity.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct candela : named_unit<candela, "cd", prefix> {};
 struct yoctocandela : prefixed_unit<yoctocandela, yocto, candela> {};
@@ -51,7 +51,7 @@ struct exacandela : prefixed_unit<exacandela, exa, candela> {};
 struct zettacandela : prefixed_unit<zettacandela, zetta, candela> {};
 struct yottacandela : prefixed_unit<yottacandela, yotta, candela> {};
 
-struct dim_luminous_intensity : physical::dim_luminous_intensity<candela> {};
+struct dim_luminous_intensity : isq::dim_luminous_intensity<candela> {};
 
 template<UnitOf<dim_luminous_intensity> U, QuantityValue Rep = double>
 using luminous_intensity = quantity<dim_luminous_intensity, U, Rep>;
@@ -170,4 +170,4 @@ inline constexpr auto Ycd = luminous_intensity<yottacandela, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/magnetic_flux.h b/src/include/units/isq/si/magnetic_flux.h
similarity index 96%
rename from src/include/units/physical/si/magnetic_flux.h
rename to src/include/units/isq/si/magnetic_flux.h
index 239ebfbe..db06f89c 100644
--- a/src/include/units/physical/si/magnetic_flux.h
+++ b/src/include/units/isq/si/magnetic_flux.h
@@ -22,12 +22,12 @@
 
 #pragma once
 
-#include <units/physical/dimensions/magnetic_flux.h>
-#include <units/physical/si/magnetic_induction.h>
-#include <units/physical/si/area.h>
+#include <units/isq/dimensions/magnetic_flux.h>
+#include <units/isq/si/magnetic_induction.h>
+#include <units/isq/si/area.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct weber : named_unit<weber, "Wb", prefix> {};
 
@@ -48,7 +48,7 @@ struct exaweber : prefixed_unit<exaweber, exa, weber> {};
 struct zettaweber : prefixed_unit<zettaweber, zetta, weber> {};
 struct yottaweber : prefixed_unit<yottaweber, yotta, weber> {};
 
-struct dim_magnetic_flux : physical::dim_magnetic_flux<dim_magnetic_flux, weber, dim_magnetic_induction, dim_area> {};
+struct dim_magnetic_flux : isq::dim_magnetic_flux<dim_magnetic_flux, weber, dim_magnetic_induction, dim_area> {};
 
 template<UnitOf<dim_magnetic_flux> U, QuantityValue Rep = double>
 using magnetic_flux = quantity<dim_magnetic_flux, U, Rep>;
@@ -147,4 +147,4 @@ inline constexpr auto YWb = magnetic_flux<yottaweber, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/magnetic_induction.h b/src/include/units/isq/si/magnetic_induction.h
similarity index 96%
rename from src/include/units/physical/si/magnetic_induction.h
rename to src/include/units/isq/si/magnetic_induction.h
index ead487b8..ef46d3f5 100644
--- a/src/include/units/physical/si/magnetic_induction.h
+++ b/src/include/units/isq/si/magnetic_induction.h
@@ -22,14 +22,14 @@
 
 #pragma once
 
-#include <units/physical/dimensions/magnetic_induction.h>
-#include <units/physical/si/voltage.h>
-#include <units/physical/si/time.h>
-#include <units/physical/si/length.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/magnetic_induction.h>
+#include <units/isq/si/voltage.h>
+#include <units/isq/si/time.h>
+#include <units/isq/si/length.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct tesla : named_unit<tesla, "T", prefix> {};
 
@@ -52,7 +52,7 @@ struct yottatesla : prefixed_unit<yottatesla, yotta, tesla> {};
 
 struct gauss : named_scaled_unit<gauss, "G", prefix, ratio(1, 10'000), tesla> {};
 
-struct dim_magnetic_induction : physical::dim_magnetic_induction<dim_magnetic_induction, tesla, dim_voltage, dim_time, dim_length> {};
+struct dim_magnetic_induction : isq::dim_magnetic_induction<dim_magnetic_induction, tesla, dim_voltage, dim_time, dim_length> {};
 
 template<UnitOf<dim_magnetic_induction> U, QuantityValue Rep = double>
 using magnetic_induction = quantity<dim_magnetic_induction, U, Rep>;
diff --git a/src/include/units/physical/si/mass.h b/src/include/units/isq/si/mass.h
similarity index 98%
rename from src/include/units/physical/si/mass.h
rename to src/include/units/isq/si/mass.h
index 13fd88b7..f2ce0977 100644
--- a/src/include/units/physical/si/mass.h
+++ b/src/include/units/isq/si/mass.h
@@ -23,11 +23,11 @@
 #pragma once
 
 #include <units/one_rep.h>
-#include <units/physical/dimensions/mass.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/mass.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct gram : named_unit<gram, "g", prefix> {};
 struct yoctogram : prefixed_unit<yoctogram, yocto, gram> {};
@@ -75,7 +75,7 @@ struct yottatonne : prefixed_unit<yottatonne, yotta, tonne> {};
 
 struct dalton : named_scaled_unit<dalton, "Da", no_prefix, ratio(16'605'390'666'050, 10'000'000'000'000, -27), kilogram> {};
 
-struct dim_mass : physical::dim_mass<kilogram> {};
+struct dim_mass : isq::dim_mass<kilogram> {};
 
 template<UnitOf<dim_mass> U, QuantityValue Rep = double>
 using mass = quantity<dim_mass, U, Rep>;
@@ -304,4 +304,4 @@ inline constexpr auto Da = mass<dalton, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/molar_energy.h b/src/include/units/isq/si/molar_energy.h
similarity index 82%
rename from src/include/units/physical/si/molar_energy.h
rename to src/include/units/isq/si/molar_energy.h
index 4f347556..9fd7728a 100644
--- a/src/include/units/physical/si/molar_energy.h
+++ b/src/include/units/isq/si/molar_energy.h
@@ -22,17 +22,17 @@
 
 #pragma once
 
-#include <units/physical/dimensions/molar_energy.h>
-#include <units/physical/si/energy.h>
-#include <units/physical/si/amount_of_substance.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/molar_energy.h>
+#include <units/isq/si/energy.h>
+#include <units/isq/si/amount_of_substance.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct joule_per_mole : unit<joule_per_mole> {};
 
-struct dim_molar_energy : physical::dim_molar_energy<dim_molar_energy, joule_per_mole, dim_energy, dim_amount_of_substance> {};
+struct dim_molar_energy : isq::dim_molar_energy<dim_molar_energy, joule_per_mole, dim_energy, dim_amount_of_substance> {};
 
 template<UnitOf<dim_molar_energy> U, QuantityValue Rep = double>
 using molar_energy = quantity<dim_molar_energy, U, Rep>;
@@ -45,4 +45,4 @@ constexpr auto operator"" _q_J_per_mol(long double l) { return molar_energy<joul
 
 }  // namespace literals
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/momentum.h b/src/include/units/isq/si/momentum.h
similarity index 85%
rename from src/include/units/physical/si/momentum.h
rename to src/include/units/isq/si/momentum.h
index 70542d12..2c5bb3eb 100644
--- a/src/include/units/physical/si/momentum.h
+++ b/src/include/units/isq/si/momentum.h
@@ -22,15 +22,15 @@
 
 #pragma once
 
-#include <units/physical/dimensions/momentum.h>
-#include <units/physical/si/mass.h>
-#include <units/physical/si/speed.h>
+#include <units/isq/dimensions/momentum.h>
+#include <units/isq/si/mass.h>
+#include <units/isq/si/speed.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct kilogram_metre_per_second : unit<kilogram_metre_per_second> {};
-struct dim_momentum : physical::dim_momentum<dim_momentum, kilogram_metre_per_second, dim_mass, dim_speed> {};
+struct dim_momentum : isq::dim_momentum<dim_momentum, kilogram_metre_per_second, dim_mass, dim_speed> {};
 
 template<UnitOf<dim_momentum> U, QuantityValue Rep = double>
 using momentum = quantity<dim_momentum, U, Rep>;
@@ -43,4 +43,4 @@ constexpr auto operator"" _q_kg_m_per_s(long double l) { return momentum<kilogra
 
 }  // namespace literals
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/permeability.h b/src/include/units/isq/si/permeability.h
similarity index 84%
rename from src/include/units/physical/si/permeability.h
rename to src/include/units/isq/si/permeability.h
index 7fd335f3..2510ce9d 100644
--- a/src/include/units/physical/si/permeability.h
+++ b/src/include/units/isq/si/permeability.h
@@ -22,16 +22,16 @@
 
 #pragma once
 
-#include <units/physical/dimensions/permeability.h>
-#include <units/physical/si/inductance.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/permeability.h>
+#include <units/isq/si/inductance.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct henry_per_metre : unit<henry_per_metre> {};
 
-struct dim_permeability : physical::dim_permeability<dim_permeability, henry_per_metre, dim_inductance, dim_length> {};
+struct dim_permeability : isq::dim_permeability<dim_permeability, henry_per_metre, dim_inductance, dim_length> {};
 
 template<UnitOf<dim_permeability> U, QuantityValue Rep = double>
 using permeability = quantity<dim_permeability, U, Rep>;
@@ -44,5 +44,5 @@ constexpr auto operator"" _q_H_per_m(long double l) { return permeability<henry_
 
 }  // namespace literals
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
 
diff --git a/src/include/units/physical/si/permittivity.h b/src/include/units/isq/si/permittivity.h
similarity index 84%
rename from src/include/units/physical/si/permittivity.h
rename to src/include/units/isq/si/permittivity.h
index 3702c05a..a141dee3 100644
--- a/src/include/units/physical/si/permittivity.h
+++ b/src/include/units/isq/si/permittivity.h
@@ -22,16 +22,16 @@
 
 #pragma once
 
-#include <units/physical/dimensions/permittivity.h>
-#include <units/physical/si/capacitance.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/permittivity.h>
+#include <units/isq/si/capacitance.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct farad_per_metre : unit<farad_per_metre> {};
 
-struct dim_permittivity : physical::dim_permittivity<dim_permittivity, farad_per_metre, dim_capacitance, dim_length> {};
+struct dim_permittivity : isq::dim_permittivity<dim_permittivity, farad_per_metre, dim_capacitance, dim_length> {};
 
 template<UnitOf<dim_permittivity> U, QuantityValue Rep = double>
 using permittivity = quantity<dim_permittivity, U, Rep>;
@@ -44,5 +44,5 @@ constexpr auto operator"" _q_F_per_m(long double l) { return permittivity<farad_
 
 }  // namespace literals
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
 
diff --git a/src/include/units/physical/si/power.h b/src/include/units/isq/si/power.h
similarity index 96%
rename from src/include/units/physical/si/power.h
rename to src/include/units/isq/si/power.h
index 17e323e2..dd2278a1 100644
--- a/src/include/units/physical/si/power.h
+++ b/src/include/units/isq/si/power.h
@@ -22,12 +22,12 @@
 
 #pragma once
 
-#include <units/physical/dimensions/power.h>
-#include <units/physical/si/energy.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/power.h>
+#include <units/isq/si/energy.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct watt : named_unit<watt, "W", prefix> {};
 struct yoctowatt : prefixed_unit<yoctowatt, yocto, watt> {};
@@ -47,7 +47,7 @@ struct exawatt : prefixed_unit<exawatt, exa, watt> {};
 struct zettawatt : prefixed_unit<zettawatt, zetta, watt> {};
 struct yottawatt : prefixed_unit<yottawatt, yotta, watt> {};
 
-struct dim_power : physical::dim_power<dim_power, watt, dim_energy, dim_time> {};
+struct dim_power : isq::dim_power<dim_power, watt, dim_energy, dim_time> {};
 
 template<UnitOf<dim_power> U, QuantityValue Rep = double>
 using power = quantity<dim_power, U, Rep>;
@@ -146,4 +146,4 @@ inline constexpr auto YW = power<yottawatt, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/prefixes.h b/src/include/units/isq/si/prefixes.h
similarity index 97%
rename from src/include/units/physical/si/prefixes.h
rename to src/include/units/isq/si/prefixes.h
index 8b0cacc6..a6e9cd08 100644
--- a/src/include/units/physical/si/prefixes.h
+++ b/src/include/units/isq/si/prefixes.h
@@ -24,7 +24,7 @@
 
 #include <units/prefix.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct prefix : prefix_family {};
 
@@ -51,4 +51,4 @@ struct zetta  : units::prefix<zetta,  prefix, "Z",             ratio(1, 1,  21)>
 struct yotta  : units::prefix<yotta,  prefix, "Y",             ratio(1, 1,  24)> {};
 // clang-format on
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/pressure.h b/src/include/units/isq/si/pressure.h
similarity index 96%
rename from src/include/units/physical/si/pressure.h
rename to src/include/units/isq/si/pressure.h
index c16feb01..c4784edf 100644
--- a/src/include/units/physical/si/pressure.h
+++ b/src/include/units/isq/si/pressure.h
@@ -22,13 +22,13 @@
 
 #pragma once
 
-#include <units/physical/dimensions/pressure.h>
-#include <units/physical/si/area.h>
-#include <units/physical/si/force.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/pressure.h>
+#include <units/isq/si/area.h>
+#include <units/isq/si/force.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct pascal : named_unit<pascal, "Pa", prefix> {};
 struct yoctopascal : prefixed_unit<yoctopascal, yocto, pascal> {};
@@ -52,7 +52,7 @@ struct exapascal : prefixed_unit<exapascal, exa, pascal> {};
 struct zettapascal : prefixed_unit<zettapascal, zetta, pascal> {};
 struct yottapascal : prefixed_unit<yottapascal, yotta, pascal> {};
 
-struct dim_pressure : physical::dim_pressure<dim_pressure, pascal, dim_force, dim_area> {};
+struct dim_pressure : isq::dim_pressure<dim_pressure, pascal, dim_force, dim_area> {};
 
 template<UnitOf<dim_pressure> U, QuantityValue Rep = double>
 using pressure = quantity<dim_pressure, U, Rep>;
@@ -171,4 +171,4 @@ inline constexpr auto YPa = pressure<yottapascal, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/radioactivity.h b/src/include/units/isq/si/radioactivity.h
similarity index 97%
rename from src/include/units/physical/si/radioactivity.h
rename to src/include/units/isq/si/radioactivity.h
index 95c9a28d..ea2c5287 100644
--- a/src/include/units/physical/si/radioactivity.h
+++ b/src/include/units/isq/si/radioactivity.h
@@ -22,11 +22,11 @@
 
 #pragma once
 
-#include <units/physical/dimensions/radioactivity.h>
-#include <units/physical/si/time.h>
+#include <units/isq/dimensions/radioactivity.h>
+#include <units/isq/si/time.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct becquerel : named_unit<becquerel, "Bq", prefix> {};
 struct yoctobecquerel : prefixed_unit<yoctobecquerel, yocto, becquerel> {};
@@ -50,7 +50,7 @@ struct exabecquerel : prefixed_unit<exabecquerel, exa, becquerel> {};
 struct zettabecquerel : prefixed_unit<zettabecquerel, zetta, becquerel> {};
 struct yottabecquerel : prefixed_unit<yottabecquerel, yotta, becquerel> {};
 
-struct dim_radioactivity : physical::dim_radioactivity<dim_radioactivity, becquerel, dim_time> {};
+struct dim_radioactivity : isq::dim_radioactivity<dim_radioactivity, becquerel, dim_time> {};
 
 template<UnitOf<dim_radioactivity> U, QuantityValue Rep = double>
 using radioactivity = quantity<dim_radioactivity, U, Rep>;
@@ -169,4 +169,4 @@ inline constexpr auto YBq = radioactivity<yottabecquerel, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/resistance.h b/src/include/units/isq/si/resistance.h
similarity index 95%
rename from src/include/units/physical/si/resistance.h
rename to src/include/units/isq/si/resistance.h
index 94e94446..a7b2cb11 100644
--- a/src/include/units/physical/si/resistance.h
+++ b/src/include/units/isq/si/resistance.h
@@ -22,13 +22,13 @@
 
 #pragma once
 
-#include <units/physical/dimensions/resistance.h>
-#include <units/physical/si/voltage.h>
-#include <units/physical/si/electric_current.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/resistance.h>
+#include <units/isq/si/voltage.h>
+#include <units/isq/si/electric_current.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct ohm : named_unit<ohm, basic_symbol_text{"Ω", "ohm"}, prefix> {};
 struct yoctoohm : prefixed_unit<yoctoohm, yocto, ohm> {};
@@ -48,7 +48,7 @@ struct exaohm : prefixed_unit<exaohm, exa, ohm> {};
 struct zettaohm : prefixed_unit<zettaohm, zetta, ohm> {};
 struct yottaohm : prefixed_unit<yottaohm, yotta, ohm> {};
 
-struct dim_resistance : physical::dim_resistance<dim_resistance, ohm, dim_voltage, dim_electric_current> {};
+struct dim_resistance : isq::dim_resistance<dim_resistance, ohm, dim_voltage, dim_electric_current> {};
 
 template<UnitOf<dim_resistance> U, QuantityValue Rep = double>
 using resistance = quantity<dim_resistance, U, Rep>;
@@ -147,4 +147,4 @@ inline constexpr auto YR = resistance<yottaohm, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/isq/si/si.h b/src/include/units/isq/si/si.h
new file mode 100644
index 00000000..d56852a3
--- /dev/null
+++ b/src/include/units/isq/si/si.h
@@ -0,0 +1,74 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2018 Mateusz Pusz
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#pragma once
+
+#include <units/isq/si/electric_current.h>
+#include <units/isq/si/length.h>
+#include <units/isq/si/luminous_intensity.h>
+#include <units/isq/si/mass.h>
+#include <units/isq/si/amount_of_substance.h>
+#include <units/isq/si/thermodynamic_temperature.h>
+#include <units/isq/si/time.h>
+
+#include <units/isq/si/absorbed_dose.h>
+#include <units/isq/si/acceleration.h>
+#include <units/isq/si/angular_velocity.h>
+#include <units/isq/si/area.h>
+#include <units/isq/si/capacitance.h>
+#include <units/isq/si/catalytic_activity.h>
+#include <units/isq/si/charge_density.h>
+#include <units/isq/si/concentration.h>
+#include <units/isq/si/conductance.h>
+#include <units/isq/si/current_density.h>
+#include <units/isq/si/density.h>
+#include <units/isq/si/dynamic_viscosity.h>
+#include <units/isq/si/electric_charge.h>
+#include <units/isq/si/electric_field_strength.h>
+#include <units/isq/si/energy.h>
+// TODO Add when downcasting issue is solved (collides with pressure)
+// #include <units/isq/si/energy_density.h>
+#include <units/isq/si/force.h>
+#include <units/isq/si/frequency.h>
+#include <units/isq/si/heat_capacity.h>
+#include <units/isq/si/inductance.h>
+#include <units/isq/si/luminance.h>
+#include <units/isq/si/magnetic_flux.h>
+#include <units/isq/si/magnetic_induction.h>
+#include <units/isq/si/molar_energy.h>
+#include <units/isq/si/momentum.h>
+#include <units/isq/si/permeability.h>
+#include <units/isq/si/permittivity.h>
+#include <units/isq/si/power.h>
+#include <units/isq/si/pressure.h>
+// TODO Add when downcasting issue is solved (collides with frequency)
+// #include <units/isq/si/radioactivity.h>
+#include <units/isq/si/resistance.h>
+#include <units/isq/si/speed.h>
+#include <units/isq/si/surface_tension.h>
+#include <units/isq/si/thermal_conductivity.h>
+#include <units/isq/si/torque.h>
+#include <units/isq/si/voltage.h>
+#include <units/isq/si/volume.h>
+
+#include <units/isq/si/constants.h>
+#include <units/isq/si/prefixes.h>
diff --git a/src/include/units/physical/si/speed.h b/src/include/units/isq/si/speed.h
similarity index 88%
rename from src/include/units/physical/si/speed.h
rename to src/include/units/isq/si/speed.h
index e34965b2..a75c8221 100644
--- a/src/include/units/physical/si/speed.h
+++ b/src/include/units/isq/si/speed.h
@@ -22,15 +22,15 @@
 
 #pragma once
 
-#include <units/physical/dimensions/speed.h>
-#include <units/physical/si/length.h>
-#include <units/physical/si/time.h>
+#include <units/isq/dimensions/speed.h>
+#include <units/isq/si/length.h>
+#include <units/isq/si/time.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct metre_per_second : unit<metre_per_second> {};
-struct dim_speed : physical::dim_speed<dim_speed, metre_per_second, dim_length, dim_time> {};
+struct dim_speed : isq::dim_speed<dim_speed, metre_per_second, dim_length, dim_time> {};
 
 struct kilometre_per_hour : deduced_unit<kilometre_per_hour, dim_speed, kilometre, hour> {};
 
@@ -49,4 +49,4 @@ constexpr auto operator"" _q_km_per_h(long double l) { return speed<kilometre_pe
 
 }  // namespace literals
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/surface_tension.h b/src/include/units/isq/si/surface_tension.h
similarity index 85%
rename from src/include/units/physical/si/surface_tension.h
rename to src/include/units/isq/si/surface_tension.h
index 81934cd3..b82152ea 100644
--- a/src/include/units/physical/si/surface_tension.h
+++ b/src/include/units/isq/si/surface_tension.h
@@ -22,15 +22,15 @@
 
 #pragma once
 
-#include <units/physical/dimensions/surface_tension.h>
-#include <units/physical/si/force.h>
+#include <units/isq/dimensions/surface_tension.h>
+#include <units/isq/si/force.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct newton_per_metre : unit<newton_per_metre> {};
 
-struct dim_surface_tension : physical::dim_surface_tension<dim_surface_tension, newton_per_metre, dim_force, dim_length> {};
+struct dim_surface_tension : isq::dim_surface_tension<dim_surface_tension, newton_per_metre, dim_force, dim_length> {};
 
 template<UnitOf<dim_surface_tension> U, QuantityValue Rep = double>
 using surface_tension = quantity<dim_surface_tension, U, Rep>;
@@ -43,4 +43,4 @@ constexpr auto operator"" _q_N_per_m(long double l) { return surface_tension<new
 
 }  // namespace literals
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/thermal_conductivity.h b/src/include/units/isq/si/thermal_conductivity.h
similarity index 81%
rename from src/include/units/physical/si/thermal_conductivity.h
rename to src/include/units/isq/si/thermal_conductivity.h
index 54449a07..71f0cda5 100644
--- a/src/include/units/physical/si/thermal_conductivity.h
+++ b/src/include/units/isq/si/thermal_conductivity.h
@@ -22,16 +22,16 @@
 
 #pragma once
 
-#include <units/physical/dimensions/thermal_conductivity.h>
-#include <units/physical/si/power.h>
-#include <units/physical/si/thermodynamic_temperature.h>
+#include <units/isq/dimensions/thermal_conductivity.h>
+#include <units/isq/si/power.h>
+#include <units/isq/si/thermodynamic_temperature.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct watt_per_metre_kelvin : unit<watt_per_metre_kelvin> {};
 
-struct dim_thermal_conductivity : physical::dim_thermal_conductivity<dim_thermal_conductivity, watt_per_metre_kelvin, dim_power, dim_length, dim_thermodynamic_temperature> {};
+struct dim_thermal_conductivity : isq::dim_thermal_conductivity<dim_thermal_conductivity, watt_per_metre_kelvin, dim_power, dim_length, dim_thermodynamic_temperature> {};
 
 template<UnitOf<dim_thermal_conductivity> U, QuantityValue Rep = double>
 using thermal_conductivity = quantity<dim_thermal_conductivity, U, Rep>;
@@ -44,4 +44,4 @@ constexpr auto operator"" _q_W_per_m_K(long double l) { return thermal_conductiv
 
 }  // namespace literals
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/thermodynamic_temperature.h b/src/include/units/isq/si/thermodynamic_temperature.h
similarity index 89%
rename from src/include/units/physical/si/thermodynamic_temperature.h
rename to src/include/units/isq/si/thermodynamic_temperature.h
index 83c90d66..a6708fb1 100644
--- a/src/include/units/physical/si/thermodynamic_temperature.h
+++ b/src/include/units/isq/si/thermodynamic_temperature.h
@@ -23,14 +23,14 @@
 #pragma once
 
 #include <units/one_rep.h>
-#include <units/physical/dimensions/thermodynamic_temperature.h>
+#include <units/isq/dimensions/thermodynamic_temperature.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct kelvin : named_unit<kelvin, "K", no_prefix> {};
 
-struct dim_thermodynamic_temperature : physical::dim_thermodynamic_temperature<kelvin> {};
+struct dim_thermodynamic_temperature : isq::dim_thermodynamic_temperature<kelvin> {};
 
 template<UnitOf<dim_thermodynamic_temperature> U, QuantityValue Rep = double>
 using thermodynamic_temperature = quantity<dim_thermodynamic_temperature, U, Rep>;
@@ -49,4 +49,4 @@ inline constexpr auto K = thermodynamic_temperature<kelvin, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/time.h b/src/include/units/isq/si/time.h
similarity index 96%
rename from src/include/units/physical/si/time.h
rename to src/include/units/isq/si/time.h
index 9bdf871a..c7d6e552 100644
--- a/src/include/units/physical/si/time.h
+++ b/src/include/units/isq/si/time.h
@@ -23,11 +23,11 @@
 #pragma once
 
 #include <units/one_rep.h>
-#include <units/physical/dimensions/time.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/time.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct second : named_unit<second, "s", prefix> {};
 struct yoctosecond : prefixed_unit<yoctosecond, yocto, second> {};
@@ -42,7 +42,7 @@ struct minute : named_scaled_unit<minute, "min", no_prefix, ratio(60), second> {
 struct hour : named_scaled_unit<hour, "h", no_prefix, ratio(60), minute> {};
 struct day : named_scaled_unit<day, "d", no_prefix, ratio(24), hour> {};
 
-struct dim_time : physical::dim_time<second> {};
+struct dim_time : isq::dim_time<second> {};
 
 template<UnitOf<dim_time> U, QuantityValue Rep = double>
 using time = quantity<dim_time, U, Rep>;
@@ -116,4 +116,4 @@ inline constexpr auto d = time<day, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/torque.h b/src/include/units/isq/si/torque.h
similarity index 86%
rename from src/include/units/physical/si/torque.h
rename to src/include/units/isq/si/torque.h
index 2bb4bf74..7728da40 100644
--- a/src/include/units/physical/si/torque.h
+++ b/src/include/units/isq/si/torque.h
@@ -22,17 +22,17 @@
 
 #pragma once
 
-#include <units/physical/dimensions/torque.h>
-#include <units/physical/si/energy.h>
+#include <units/isq/dimensions/torque.h>
+#include <units/isq/si/energy.h>
 #include <units/generic/angle.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct newton_metre_per_radian : unit<newton_metre_per_radian> {};
 
-struct dim_torque : physical::dim_torque<dim_torque, newton_metre_per_radian, dim_force, dim_length, dim_angle<>> {};
+struct dim_torque : isq::dim_torque<dim_torque, newton_metre_per_radian, dim_force, dim_length, dim_angle<>> {};
 
 template<UnitOf<dim_torque> U, QuantityValue Rep = double>
 using torque = quantity<dim_torque, U, Rep>;
@@ -51,4 +51,4 @@ inline constexpr auto Nm_per_rad = torque<newton_metre_per_radian, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/typographic/length.h b/src/include/units/isq/si/typographic/length.h
similarity index 96%
rename from src/include/units/physical/si/typographic/length.h
rename to src/include/units/isq/si/typographic/length.h
index dc9eade9..b3a57cfd 100644
--- a/src/include/units/physical/si/typographic/length.h
+++ b/src/include/units/isq/si/typographic/length.h
@@ -23,9 +23,9 @@
 
 #pragma once
 
-#include <units/physical/si/length.h>
+#include <units/isq/si/length.h>
 
-namespace units::physical::si::typographic {
+namespace units::isq::si::typographic {
 
 // TODO Conflicts with (https://en.wikipedia.org/wiki/Pica_(typography)), verify correctness of below conversion factors and provide hyperlinks to definitions
 struct pica_comp : named_scaled_unit<pica_comp, "pica(comp)", no_prefix, ratio(4233333, 1000000, -3), si::metre> {};
@@ -62,4 +62,4 @@ inline constexpr auto point_prn = si::length<typographic::point_prn, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::typographic
+}  // namespace units::isq::si::typographic
diff --git a/src/include/units/physical/si/typographic/typographic.h b/src/include/units/isq/si/typographic/typographic.h
similarity index 95%
rename from src/include/units/physical/si/typographic/typographic.h
rename to src/include/units/isq/si/typographic/typographic.h
index 994bb64d..a5d4a789 100644
--- a/src/include/units/physical/si/typographic/typographic.h
+++ b/src/include/units/isq/si/typographic/typographic.h
@@ -22,4 +22,4 @@
 
 #pragma once
 
-#include <units/physical/si/typographic/length.h>
+#include <units/isq/si/typographic/length.h>
diff --git a/src/include/units/physical/si/us/length.h b/src/include/units/isq/si/us/length.h
similarity index 76%
rename from src/include/units/physical/si/us/length.h
rename to src/include/units/isq/si/us/length.h
index 0340c960..3ac5fbc4 100644
--- a/src/include/units/physical/si/us/length.h
+++ b/src/include/units/isq/si/us/length.h
@@ -22,9 +22,9 @@
 
 #pragma once
 
-#include <units/physical/si/length.h>
+#include <units/isq/si/length.h>
 
-namespace units::physical::si::us {
+namespace units::isq::si::us {
 
 // https://en.wikipedia.org/wiki/Foot_(unit)#US_survey_foot
 // https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors#B6
@@ -40,25 +40,25 @@ struct mile : named_scaled_unit<mile, "mi(us)", no_prefix, ratio(5280), foot> {}
 inline namespace literals {
 
 // ft
-constexpr auto operator"" _q_ft_us(unsigned long long l) { gsl_ExpectsAudit(std::in_range<std::int64_t>(l)); return si::length<units::physical::si::us::foot, std::int64_t>(static_cast<std::int64_t>(l)); }
-constexpr auto operator"" _q_ft_us(long double l) { return si::length<units::physical::si::us::foot, long double>(l); }
+constexpr auto operator"" _q_ft_us(unsigned long long l) { gsl_ExpectsAudit(std::in_range<std::int64_t>(l)); return si::length<units::isq::si::us::foot, std::int64_t>(static_cast<std::int64_t>(l)); }
+constexpr auto operator"" _q_ft_us(long double l) { return si::length<units::isq::si::us::foot, long double>(l); }
 
 // fathom
-constexpr auto operator"" _q_fathom_us(unsigned long long l) { gsl_ExpectsAudit(std::in_range<std::int64_t>(l)); return si::length<units::physical::si::us::fathom, std::int64_t>(static_cast<std::int64_t>(l)); }
-constexpr auto operator"" _q_fathom_us(long double l) { return si::length<units::physical::si::us::fathom, long double>(l); }
+constexpr auto operator"" _q_fathom_us(unsigned long long l) { gsl_ExpectsAudit(std::in_range<std::int64_t>(l)); return si::length<units::isq::si::us::fathom, std::int64_t>(static_cast<std::int64_t>(l)); }
+constexpr auto operator"" _q_fathom_us(long double l) { return si::length<units::isq::si::us::fathom, long double>(l); }
 
 // mi
-constexpr auto operator"" _q_mi_us(unsigned long long l) { gsl_ExpectsAudit(std::in_range<std::int64_t>(l)); return si::length<units::physical::si::us::mile, std::int64_t>(static_cast<std::int64_t>(l)); }
-constexpr auto operator"" _q_mi_us(long double l) { return si::length<units::physical::si::us::mile, long double>(l); }
+constexpr auto operator"" _q_mi_us(unsigned long long l) { gsl_ExpectsAudit(std::in_range<std::int64_t>(l)); return si::length<units::isq::si::us::mile, std::int64_t>(static_cast<std::int64_t>(l)); }
+constexpr auto operator"" _q_mi_us(long double l) { return si::length<units::isq::si::us::mile, long double>(l); }
 
 }  // namespace literals
 
 namespace unit_constants {
 
-inline constexpr auto ft = si::length<units::physical::si::us::foot, one_rep>{};
-inline constexpr auto fathom = si::length<units::physical::si::us::fathom, one_rep>{};
-inline constexpr auto mi = si::length<units::physical::si::us::mile, one_rep>{};
+inline constexpr auto ft = si::length<units::isq::si::us::foot, one_rep>{};
+inline constexpr auto fathom = si::length<units::isq::si::us::fathom, one_rep>{};
+inline constexpr auto mi = si::length<units::isq::si::us::mile, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si::us
+}  // namespace units::isq::si::us
diff --git a/src/include/units/physical/si/us/us.h b/src/include/units/isq/si/us/us.h
similarity index 96%
rename from src/include/units/physical/si/us/us.h
rename to src/include/units/isq/si/us/us.h
index fe68840b..556b5fa0 100644
--- a/src/include/units/physical/si/us/us.h
+++ b/src/include/units/isq/si/us/us.h
@@ -22,4 +22,4 @@
 
 #pragma once
 
-#include <units/physical/si/us/length.h>
+#include <units/isq/si/us/length.h>
diff --git a/src/include/units/physical/si/voltage.h b/src/include/units/isq/si/voltage.h
similarity index 96%
rename from src/include/units/physical/si/voltage.h
rename to src/include/units/isq/si/voltage.h
index 0f84f161..df866979 100644
--- a/src/include/units/physical/si/voltage.h
+++ b/src/include/units/isq/si/voltage.h
@@ -22,13 +22,13 @@
 
 #pragma once
 
-#include <units/physical/dimensions/voltage.h>
-#include <units/physical/si/electric_current.h>
-#include <units/physical/si/power.h>
-#include <units/physical/si/prefixes.h>
+#include <units/isq/dimensions/voltage.h>
+#include <units/isq/si/electric_current.h>
+#include <units/isq/si/power.h>
+#include <units/isq/si/prefixes.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct volt : named_unit<volt, "V", prefix> {};
 struct yoctovolt : prefixed_unit<yoctovolt, yocto, volt> {};
@@ -52,7 +52,7 @@ struct exavolt : prefixed_unit<exavolt, exa, volt> {};
 struct zettavolt : prefixed_unit<zettavolt, zetta, volt> {};
 struct yottavolt : prefixed_unit<yottavolt, yotta, volt> {};
 
-struct dim_voltage : physical::dim_voltage<dim_voltage, volt, dim_power, dim_electric_current> {};
+struct dim_voltage : isq::dim_voltage<dim_voltage, volt, dim_power, dim_electric_current> {};
 
 template<UnitOf<dim_voltage> U, QuantityValue Rep = double>
 using voltage = quantity<dim_voltage, U, Rep>;
@@ -171,4 +171,4 @@ inline constexpr auto YV = voltage<yottavolt, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/physical/si/volume.h b/src/include/units/isq/si/volume.h
similarity index 98%
rename from src/include/units/physical/si/volume.h
rename to src/include/units/isq/si/volume.h
index 9c2ec171..fee448a8 100644
--- a/src/include/units/physical/si/volume.h
+++ b/src/include/units/isq/si/volume.h
@@ -22,14 +22,14 @@
 
 #pragma once
 
-#include <units/physical/dimensions/volume.h>
-#include <units/physical/si/length.h>
+#include <units/isq/dimensions/volume.h>
+#include <units/isq/si/length.h>
 #include <units/quantity.h>
 
-namespace units::physical::si {
+namespace units::isq::si {
 
 struct cubic_metre : unit<cubic_metre> {};
-struct dim_volume : physical::dim_volume<dim_volume, cubic_metre, dim_length> {};
+struct dim_volume : isq::dim_volume<dim_volume, cubic_metre, dim_length> {};
 
 struct cubic_yoctometre : deduced_unit<cubic_yoctometre, dim_volume, yoctometre> {};
 struct cubic_zeptometre : deduced_unit<cubic_zeptometre, dim_volume, zeptometre> {};
@@ -296,4 +296,4 @@ inline constexpr auto Yl = volume<yottalitre, one_rep>{};
 
 }  // namespace unit_constants
 
-}  // namespace units::physical::si
+}  // namespace units::isq::si
diff --git a/src/include/units/one_rep.h b/src/include/units/one_rep.h
index aba4faa1..326864e9 100644
--- a/src/include/units/one_rep.h
+++ b/src/include/units/one_rep.h
@@ -47,7 +47,7 @@ struct invalid_one_rep {};
  * Unit constants simplify quantity creation:
  * 
  * @code{.cpp}
- * using namespace units::physical::si::unit_constants;
+ * using namespace units::isq::si::unit_constants;
  *
  * auto d = 123 * m;
  * auto v = 70 * km / h;
diff --git a/src/include/units/physical/dimensions.h b/src/include/units/physical/dimensions.h
deleted file mode 100644
index 13c53b67..00000000
--- a/src/include/units/physical/dimensions.h
+++ /dev/null
@@ -1,70 +0,0 @@
-// The MIT License (MIT)
-//
-// Copyright (c) 2018 Mateusz Pusz
-//
-// Permission is hereby granted, free of charge, to any person obtaining a copy
-// of this software and associated documentation files (the "Software"), to deal
-// in the Software without restriction, including without limitation the rights
-// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-// copies of the Software, and to permit persons to whom the Software is
-// furnished to do so, subject to the following conditions:
-//
-// The above copyright notice and this permission notice shall be included in all
-// copies or substantial portions of the Software.
-//
-// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-// SOFTWARE.
-
-#pragma once
-
-#include <units/physical/dimensions/absorbed_dose.h>
-#include <units/physical/dimensions/acceleration.h>
-#include <units/physical/dimensions/amount_of_substance.h>
-#include <units/physical/dimensions/angular_velocity.h>
-#include <units/physical/dimensions/area.h>
-#include <units/physical/dimensions/capacitance.h>
-#include <units/physical/dimensions/catalytic_activity.h>
-#include <units/physical/dimensions/charge_density.h>
-#include <units/physical/dimensions/concentration.h>
-#include <units/physical/dimensions/conductance.h>
-#include <units/physical/dimensions/current_density.h>
-#include <units/physical/dimensions/density.h>
-#include <units/physical/dimensions/dynamic_viscosity.h>
-#include <units/physical/dimensions/electric_charge.h>
-#include <units/physical/dimensions/electric_current.h>
-#include <units/physical/dimensions/electric_field_strength.h>
-#include <units/physical/dimensions/energy.h>
-// TODO Add when downcasting issue is solved (collides with pressure)
-// #include <units/physical/dimensions/energy_density.h>
-#include <units/physical/dimensions/force.h>
-#include <units/physical/dimensions/frequency.h>
-#include <units/physical/dimensions/heat_capacity.h>
-#include <units/physical/dimensions/inductance.h>
-#include <units/physical/dimensions/length.h>
-#include <units/physical/dimensions/luminance.h>
-#include <units/physical/dimensions/luminous_intensity.h>
-#include <units/physical/dimensions/magnetic_flux.h>
-#include <units/physical/dimensions/magnetic_induction.h>
-#include <units/physical/dimensions/mass.h>
-#include <units/physical/dimensions/molar_energy.h>
-#include <units/physical/dimensions/momentum.h>
-#include <units/physical/dimensions/permeability.h>
-#include <units/physical/dimensions/permittivity.h>
-#include <units/physical/dimensions/power.h>
-#include <units/physical/dimensions/pressure.h>
-// TODO Add when downcasting issue is solved (collides with frequency)
-// #include <units/physical/dimensions/radioactivity.h>
-#include <units/physical/dimensions/resistance.h>
-#include <units/physical/dimensions/speed.h>
-#include <units/physical/dimensions/surface_tension.h>
-#include <units/physical/dimensions/thermal_conductivity.h>
-#include <units/physical/dimensions/thermodynamic_temperature.h>
-#include <units/physical/dimensions/time.h>
-#include <units/physical/dimensions/torque.h>
-#include <units/physical/dimensions/voltage.h>
-#include <units/physical/dimensions/volume.h>
diff --git a/src/include/units/physical/si/cgs/cgs.h b/src/include/units/physical/si/cgs/cgs.h
deleted file mode 100644
index 690c2240..00000000
--- a/src/include/units/physical/si/cgs/cgs.h
+++ /dev/null
@@ -1,35 +0,0 @@
-// The MIT License (MIT)
-//
-// Copyright (c) 2018 Mateusz Pusz
-//
-// Permission is hereby granted, free of charge, to any person obtaining a copy
-// of this software and associated documentation files (the "Software"), to deal
-// in the Software without restriction, including without limitation the rights
-// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-// copies of the Software, and to permit persons to whom the Software is
-// furnished to do so, subject to the following conditions:
-//
-// The above copyright notice and this permission notice shall be included in all
-// copies or substantial portions of the Software.
-//
-// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-// SOFTWARE.
-
-#pragma once
-
-#include <units/physical/si/cgs/length.h>
-#include <units/physical/si/cgs/mass.h>
-#include <units/physical/si/cgs/time.h>
-
-#include <units/physical/si/cgs/acceleration.h>
-#include <units/physical/si/cgs/area.h>
-#include <units/physical/si/cgs/energy.h>
-#include <units/physical/si/cgs/force.h>
-#include <units/physical/si/cgs/power.h>
-#include <units/physical/si/cgs/pressure.h>
-#include <units/physical/si/cgs/speed.h>
diff --git a/src/include/units/physical/si/fps/fps.h b/src/include/units/physical/si/fps/fps.h
deleted file mode 100644
index 61b9350e..00000000
--- a/src/include/units/physical/si/fps/fps.h
+++ /dev/null
@@ -1,37 +0,0 @@
-// The MIT License (MIT)
-//
-// Copyright (c) 2018 Mateusz Pusz
-//
-// Permission is hereby granted, free of charge, to any person obtaining a copy
-// of this software and associated documentation files (the "Software"), to deal
-// in the Software without restriction, including without limitation the rights
-// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-// copies of the Software, and to permit persons to whom the Software is
-// furnished to do so, subject to the following conditions:
-//
-// The above copyright notice and this permission notice shall be included in all
-// copies or substantial portions of the Software.
-//
-// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-// SOFTWARE.
-
-#pragma once
-
-#include <units/physical/si/fps/length.h>
-#include <units/physical/si/fps/mass.h>
-#include <units/physical/si/fps/time.h>
-
-#include <units/physical/si/fps/acceleration.h>
-#include <units/physical/si/fps/area.h>
-#include <units/physical/si/fps/density.h>
-#include <units/physical/si/fps/energy.h>
-#include <units/physical/si/fps/force.h>
-#include <units/physical/si/fps/power.h>
-#include <units/physical/si/fps/pressure.h>
-#include <units/physical/si/fps/speed.h>
-#include <units/physical/si/fps/volume.h>
diff --git a/src/include/units/physical/si/si.h b/src/include/units/physical/si/si.h
deleted file mode 100644
index d7c1e528..00000000
--- a/src/include/units/physical/si/si.h
+++ /dev/null
@@ -1,74 +0,0 @@
-// The MIT License (MIT)
-//
-// Copyright (c) 2018 Mateusz Pusz
-//
-// Permission is hereby granted, free of charge, to any person obtaining a copy
-// of this software and associated documentation files (the "Software"), to deal
-// in the Software without restriction, including without limitation the rights
-// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-// copies of the Software, and to permit persons to whom the Software is
-// furnished to do so, subject to the following conditions:
-//
-// The above copyright notice and this permission notice shall be included in all
-// copies or substantial portions of the Software.
-//
-// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-// SOFTWARE.
-
-#pragma once
-
-#include <units/physical/si/electric_current.h>
-#include <units/physical/si/length.h>
-#include <units/physical/si/luminous_intensity.h>
-#include <units/physical/si/mass.h>
-#include <units/physical/si/amount_of_substance.h>
-#include <units/physical/si/thermodynamic_temperature.h>
-#include <units/physical/si/time.h>
-
-#include <units/physical/si/absorbed_dose.h>
-#include <units/physical/si/acceleration.h>
-#include <units/physical/si/angular_velocity.h>
-#include <units/physical/si/area.h>
-#include <units/physical/si/capacitance.h>
-#include <units/physical/si/catalytic_activity.h>
-#include <units/physical/si/charge_density.h>
-#include <units/physical/si/concentration.h>
-#include <units/physical/si/conductance.h>
-#include <units/physical/si/current_density.h>
-#include <units/physical/si/density.h>
-#include <units/physical/si/dynamic_viscosity.h>
-#include <units/physical/si/electric_charge.h>
-#include <units/physical/si/electric_field_strength.h>
-#include <units/physical/si/energy.h>
-// TODO Add when downcasting issue is solved (collides with pressure)
-// #include <units/physical/si/energy_density.h>
-#include <units/physical/si/force.h>
-#include <units/physical/si/frequency.h>
-#include <units/physical/si/heat_capacity.h>
-#include <units/physical/si/inductance.h>
-#include <units/physical/si/luminance.h>
-#include <units/physical/si/magnetic_flux.h>
-#include <units/physical/si/magnetic_induction.h>
-#include <units/physical/si/molar_energy.h>
-#include <units/physical/si/momentum.h>
-#include <units/physical/si/permeability.h>
-#include <units/physical/si/permittivity.h>
-#include <units/physical/si/power.h>
-#include <units/physical/si/pressure.h>
-// TODO Add when downcasting issue is solved (collides with frequency)
-// #include <units/physical/si/radioactivity.h>
-#include <units/physical/si/resistance.h>
-#include <units/physical/si/speed.h>
-#include <units/physical/si/surface_tension.h>
-#include <units/physical/si/thermal_conductivity.h>
-#include <units/physical/si/torque.h>
-#include <units/physical/si/voltage.h>
-#include <units/physical/si/volume.h>
-
-#include <units/physical/si/constants.h>
-#include <units/physical/si/prefixes.h>
diff --git a/src/include/units/quantity_cast.h b/src/include/units/quantity_cast.h
index 2ca6f254..d0c48879 100644
--- a/src/include/units/quantity_cast.h
+++ b/src/include/units/quantity_cast.h
@@ -107,7 +107,7 @@ struct cast_traits<From, To> {
  *
  * This cast gets the target quantity type to cast to. For example:
  *
- * auto q1 = units::quantity_cast<units::physical::si::time<units::physical::si::second>>(1_q_ms);
+ * auto q1 = units::quantity_cast<units::isq::si::time<units::isq::si::second>>(1_q_ms);
  *
  * @tparam To a target quantity type to cast to
  */
@@ -146,7 +146,7 @@ template<Quantity To, typename D, typename U, scalable_with_<typename To::rep> R
  *
  * This cast gets only the target dimension to cast to. For example:
  *
- * auto q1 = units::quantity_cast<units::physical::si::dim_acceleration>(200_q_Gal);
+ * auto q1 = units::quantity_cast<units::isq::si::dim_acceleration>(200_q_Gal);
  *
  * @tparam ToD a dimension type to use for a target quantity
  */
@@ -165,7 +165,7 @@ template<Dimension ToD, typename D, typename U, typename Rep>
  *
  * This cast gets only the target unit to cast to. For example:
  *
- * auto q1 = units::quantity_cast<units::physical::si::second>(1_q_ms);
+ * auto q1 = units::quantity_cast<units::isq::si::second>(1_q_ms);
  *
  * @tparam ToU a unit type to use for a target quantity
  */
@@ -184,7 +184,7 @@ template<Unit ToU, typename D, typename U, typename Rep>
  *
  * This cast gets both the target dimension and unit to cast to. For example:
  *
- * auto q1 = units::quantity_cast<units::physical::si::dim_speed, units::physical::si::kilometre_per_hour>(v1);
+ * auto q1 = units::quantity_cast<units::isq::si::dim_speed, units::isq::si::kilometre_per_hour>(v1);
  *
  * @note This cast is especially useful when working with quantities of unknown dimensions
  * (@c unknown_dimension).
@@ -227,9 +227,9 @@ template<QuantityValue ToRep, typename D, typename U, scalable_with_<ToRep> Rep>
  * This cast gets the target quantity point type to cast to or anything that works for quantity_cast. For example:
  *
  * auto q1 = units::quantity_point_cast<decltype(quantity_point{0_q_s})>(quantity_point{1_q_ms});
- * auto q1 = units::quantity_point_cast<units::physical::si::time<units::physical::si::second>>(quantity_point{1_q_ms});
- * auto q1 = units::quantity_point_cast<units::physical::si::dim_acceleration>(quantity_point{200_q_Gal});
- * auto q1 = units::quantity_point_cast<units::physical::si::second>(quantity_point{1_q_ms});
+ * auto q1 = units::quantity_point_cast<units::isq::si::time<units::isq::si::second>>(quantity_point{1_q_ms});
+ * auto q1 = units::quantity_point_cast<units::isq::si::dim_acceleration>(quantity_point{200_q_Gal});
+ * auto q1 = units::quantity_point_cast<units::isq::si::second>(quantity_point{1_q_ms});
  * auto q1 = units::quantity_point_cast<int>(quantity_point{1_q_ms});
  *
  * @tparam CastSpec a target quantity point type to cast to or anything that works for quantity_cast
@@ -253,7 +253,7 @@ template<typename CastSpec, typename D, typename U, typename Rep>
  *
  * This cast gets both the target dimension and unit to cast to. For example:
  *
- * auto q1 = units::quantity_point_cast<units::physical::si::dim_speed, units::physical::si::kilometre_per_hour>(v1);
+ * auto q1 = units::quantity_point_cast<units::isq::si::dim_speed, units::isq::si::kilometre_per_hour>(v1);
  *
  * @note This cast is especially useful when working with quantity points of unknown dimensions
  * (@c unknown_dimension).
@@ -278,9 +278,9 @@ template<Dimension ToD, Unit ToU, typename D, typename U, typename Rep>
  *
  * auto q1 = units::quantity_kind_cast<decltype(ns::width{1 * m})>(quantity_kind{ns::width{1 * mm});
  * auto q1 = units::quantity_kind_cast<ns::height_kind>(ns::width{1 * m});
- * auto q1 = units::quantity_kind_cast<units::physical::si::length<units::physical::si::metre>>(ns::width{1 * mm});
- * auto q1 = units::quantity_kind_cast<units::physical::si::dim_acceleration>(ns::rate_of_climb{200 * Gal});
- * auto q1 = units::quantity_kind_cast<units::physical::si::metre>(ns::width{1 * mm});
+ * auto q1 = units::quantity_kind_cast<units::isq::si::length<units::isq::si::metre>>(ns::width{1 * mm});
+ * auto q1 = units::quantity_kind_cast<units::isq::si::dim_acceleration>(ns::rate_of_climb{200 * Gal});
+ * auto q1 = units::quantity_kind_cast<units::isq::si::metre>(ns::width{1 * mm});
  * auto q1 = units::quantity_kind_cast<int>(ns::width{1.0 * mm});
  *
  * @tparam CastSpec a target (quantity) kind type to cast to or anything that works for quantity_cast
@@ -311,7 +311,7 @@ template<typename CastSpec, typename K, typename U, typename Rep>
  *
  * This cast gets both the target kind and unit to cast to. For example:
  *
- * auto q1 = units::quantity_kind_cast<ns::height_kind, units::physical::si::kilometre>(w);
+ * auto q1 = units::quantity_kind_cast<ns::height_kind, units::isq::si::kilometre>(w);
  *
  * @note This cast is especially useful when working with quantity kinds of unknown kind.
  *
@@ -337,9 +337,9 @@ template<Kind ToK, Unit ToU, typename K, typename U, typename Rep>
  * auto q1 = units::quantity_point_kind_cast<decltype(ns::width{1 * m})>(ns::x_coordinate{1 * mm});
  * auto q1 = units::quantity_point_kind_cast<ns::y_coordinate_kind>(ns::x_coordinate{1 * m});
  * auto q1 = units::quantity_point_kind_cast<ns::height_kind>(ns::x_coordinate{1 * m});
- * auto q1 = units::quantity_point_kind_cast<units::physical::si::length<units::physical::si::metre>>(ns::x_coordinate{1 * mm});
- * auto q1 = units::quantity_point_kind_cast<units::physical::si::dim_acceleration>(quantity_point_kind(ns::rate_of_climb{200 * Gal}));
- * auto q1 = units::quantity_point_kind_cast<units::physical::si::metre>(ns::x_coordinate{1 * mm});
+ * auto q1 = units::quantity_point_kind_cast<units::isq::si::length<units::isq::si::metre>>(ns::x_coordinate{1 * mm});
+ * auto q1 = units::quantity_point_kind_cast<units::isq::si::dim_acceleration>(quantity_point_kind(ns::rate_of_climb{200 * Gal}));
+ * auto q1 = units::quantity_point_kind_cast<units::isq::si::metre>(ns::x_coordinate{1 * mm});
  * auto q1 = units::quantity_point_kind_cast<int>(ns::x_coordinate{1.0 * mm});
  *
  * @tparam CastSpec a target (quantity) point kind type to cast to or anything that works for quantity_kind_cast
@@ -367,7 +367,7 @@ template<typename CastSpec, typename PK, typename U, typename Rep>
  *
  * This cast gets both the target point kind and unit to cast to. For example:
  *
- * auto q1 = units::quantity_point_kind_cast<ns::y_coordinate_kind, units::physical::si::kilometre>(x);
+ * auto q1 = units::quantity_point_kind_cast<ns::y_coordinate_kind, units::isq::si::kilometre>(x);
  *
  * @note This cast is especially useful when working with quantity point kinds of unknown point kind.
  *
diff --git a/test/unit_test/runtime/distribution_test.cpp b/test/unit_test/runtime/distribution_test.cpp
index 03c32e21..264183ae 100644
--- a/test/unit_test/runtime/distribution_test.cpp
+++ b/test/unit_test/runtime/distribution_test.cpp
@@ -22,11 +22,11 @@
 
 #include <numeric>
 #include <units/random.h>
-#include <units/physical/si/length.h>
+#include <units/isq/si/length.h>
 #include <catch2/catch.hpp>
 
 using namespace units;
-using namespace units::physical::si;
+using namespace units::isq::si;
 
 TEST_CASE("uniform_int_distribution")
 {
diff --git a/test/unit_test/runtime/fmt_test.cpp b/test/unit_test/runtime/fmt_test.cpp
index ed6420e7..9fb94f2a 100644
--- a/test/unit_test/runtime/fmt_test.cpp
+++ b/test/unit_test/runtime/fmt_test.cpp
@@ -22,16 +22,16 @@
 
 #include <units/format.h>
 #include <units/math.h>
-#include <units/physical/si/si.h>
-#include <units/physical/si/cgs/cgs.h>
+#include <units/isq/si/si.h>
+#include <units/isq/si/cgs/cgs.h>
 #include <units/quantity_io.h>
 #include <catch2/catch.hpp>
 #include <iomanip>
 #include <sstream>
 
 using namespace units;
-using namespace units::physical;
-using namespace units::physical::si;
+using namespace units::isq;
+using namespace units::isq::si;
 using namespace Catch::Matchers;
 
 TEST_CASE("operator<< on a quantity", "[text][ostream][fmt]")
diff --git a/test/unit_test/runtime/fmt_units_test.cpp b/test/unit_test/runtime/fmt_units_test.cpp
index 0afb9593..52739764 100644
--- a/test/unit_test/runtime/fmt_units_test.cpp
+++ b/test/unit_test/runtime/fmt_units_test.cpp
@@ -21,20 +21,20 @@
 // SOFTWARE.
 
 #include "units/format.h"
-#include "units/physical/si/si.h"
-#include "units/physical/si/iau/iau.h"
-#include "units/physical/si/imperial/imperial.h"
-#include "units/physical/si/international/international.h"
-#include "units/physical/si/typographic/typographic.h"
-#include "units/physical/si/us/us.h"
+#include "units/isq/si/si.h"
+#include "units/isq/si/iau/iau.h"
+#include "units/isq/si/imperial/imperial.h"
+#include "units/isq/si/international/international.h"
+#include "units/isq/si/typographic/typographic.h"
+#include "units/isq/si/us/us.h"
 #include <catch2/catch.hpp>
 
-using namespace units::physical::si;
-using namespace units::physical::si::international;
-using namespace units::physical::si::us;
-using namespace units::physical::si::iau;
-using namespace units::physical::si::imperial;
-using namespace units::physical::si::typographic;
+using namespace units::isq::si;
+using namespace units::isq::si::international;
+using namespace units::isq::si::us;
+using namespace units::isq::si::iau;
+using namespace units::isq::si::imperial;
+using namespace units::isq::si::typographic;
 
 TEST_CASE("fmt::format on synthesized unit symbols", "[text][fmt]")
 {
diff --git a/test/unit_test/runtime/math_test.cpp b/test/unit_test/runtime/math_test.cpp
index 1fc6d777..3ac46f2a 100644
--- a/test/unit_test/runtime/math_test.cpp
+++ b/test/unit_test/runtime/math_test.cpp
@@ -21,12 +21,12 @@
 // SOFTWARE.
 
 #include "units/math.h"
-#include "units/physical/si/area.h"
-#include "units/physical/si/volume.h"
+#include "units/isq/si/area.h"
+#include "units/isq/si/volume.h"
 #include <catch2/catch.hpp>
 
 using namespace units;
-using namespace units::physical::si;
+using namespace units::isq::si;
 
 // classical
 
diff --git a/test/unit_test/static/cgs_test.cpp b/test/unit_test/static/cgs_test.cpp
index 84f3c4e4..bdb72c28 100644
--- a/test/unit_test/static/cgs_test.cpp
+++ b/test/unit_test/static/cgs_test.cpp
@@ -20,22 +20,22 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include <units/physical/si/cgs/cgs.h>
-#include <units/physical/si/acceleration.h>
-#include <units/physical/si/area.h>
-#include <units/physical/si/energy.h>
-#include <units/physical/si/force.h>
-#include <units/physical/si/length.h>
-#include <units/physical/si/mass.h>
-#include <units/physical/si/power.h>
-#include <units/physical/si/pressure.h>
-#include <units/physical/si/speed.h>
-#include <units/physical/si/time.h>
+#include <units/isq/si/cgs/cgs.h>
+#include <units/isq/si/acceleration.h>
+#include <units/isq/si/area.h>
+#include <units/isq/si/energy.h>
+#include <units/isq/si/force.h>
+#include <units/isq/si/length.h>
+#include <units/isq/si/mass.h>
+#include <units/isq/si/power.h>
+#include <units/isq/si/pressure.h>
+#include <units/isq/si/speed.h>
+#include <units/isq/si/time.h>
 
 namespace {
 
 using namespace units;
-using namespace units::physical::si::cgs;
+using namespace units::isq::si::cgs;
 
 /* ************** BASE DIMENSIONS **************** */
 
@@ -65,8 +65,8 @@ static_assert(centimetre::ratio / dimension_unit<dim_length>::ratio == ratio(1))
 static_assert((1_q_cm * 1_q_cm).count() == 1);
 static_assert((1_q_cm2).count() == 1);
 static_assert(1_q_cm * 1_q_cm == 1_q_cm2);
-static_assert(100_q_cm * 100_q_cm == area<physical::si::square_metre>(1));
-static_assert(100_q_cm * 100_q_cm == length<physical::si::metre>(1) * length<physical::si::metre>(1));
+static_assert(100_q_cm * 100_q_cm == area<isq::si::square_metre>(1));
+static_assert(100_q_cm * 100_q_cm == length<isq::si::metre>(1) * length<isq::si::metre>(1));
 static_assert(100_q_cm2 / 10_q_cm == 10_q_cm);
 
 static_assert(detail::unit_text<dim_area, square_centimetre>() == basic_symbol_text("cm²", "cm^2"));
diff --git a/test/unit_test/static/chrono_test.cpp b/test/unit_test/static/chrono_test.cpp
index 63418c2d..709fdbf5 100644
--- a/test/unit_test/static/chrono_test.cpp
+++ b/test/unit_test/static/chrono_test.cpp
@@ -22,14 +22,14 @@
 
 #include "test_tools.h"
 #include <units/chrono.h>
-#include <units/physical/si/speed.h>
+#include <units/isq/si/speed.h>
 #include <units/quantity_point.h>
 
 namespace {
 
 using namespace units;
-using namespace units::physical;
-using namespace units::physical::si::literals;
+using namespace units::isq;
+using namespace units::isq::si::literals;
 using namespace std::chrono_literals;
 using sys_seconds = std::chrono::time_point<std::chrono::system_clock, std::chrono::seconds>;
 using sys_days = std::chrono::time_point<std::chrono::system_clock,
diff --git a/test/unit_test/static/concepts_test.cpp b/test/unit_test/static/concepts_test.cpp
index ef543520..9f7edc71 100644
--- a/test/unit_test/static/concepts_test.cpp
+++ b/test/unit_test/static/concepts_test.cpp
@@ -20,9 +20,9 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include "units/physical/si/cgs/speed.h"
-#include "units/physical/si/speed.h"
-#include "units/physical/si/fps/speed.h"
+#include "units/isq/si/cgs/speed.h"
+#include "units/isq/si/speed.h"
+#include "units/isq/si/fps/speed.h"
 #include "units/quantity_point.h"
 #include "units/chrono.h"
 #include <chrono>
@@ -34,7 +34,7 @@
 namespace {
 
 using namespace units;
-using namespace units::physical;
+using namespace units::isq;
 
 // Prefix family
 
diff --git a/test/unit_test/static/custom_rep_test_min_expl.cpp b/test/unit_test/static/custom_rep_test_min_expl.cpp
index 06483dbf..f73cead8 100644
--- a/test/unit_test/static/custom_rep_test_min_expl.cpp
+++ b/test/unit_test/static/custom_rep_test_min_expl.cpp
@@ -20,7 +20,7 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include "units/physical/si/length.h"
+#include "units/isq/si/length.h"
 #include <ostream>
 
 namespace {
@@ -82,7 +82,7 @@ struct std::common_type<min_expl<Mode>, std::intmax_t> : std::type_identity<min_
 namespace {
 
 using namespace units;
-using namespace units::physical::si;
+using namespace units::isq::si;
 
 // quantity explicitly constructible (not convertible) from the representation type
 static_assert(std::constructible_from<length<metre, min_expl<>>, min_expl<>>);
diff --git a/test/unit_test/static/custom_rep_test_min_impl.cpp b/test/unit_test/static/custom_rep_test_min_impl.cpp
index 5d71ed65..8b9534de 100644
--- a/test/unit_test/static/custom_rep_test_min_impl.cpp
+++ b/test/unit_test/static/custom_rep_test_min_impl.cpp
@@ -21,7 +21,7 @@
 // SOFTWARE.
 
 #include "units/math.h"
-#include "units/physical/si/length.h"
+#include "units/isq/si/length.h"
 #include <chrono>
 #include <type_traits>
 #include <utility>
@@ -60,7 +60,7 @@ struct std::common_type<U, min_impl<T>> : std::common_type<T, U> {};
 namespace {
 
 using namespace units;
-using namespace units::physical::si;
+using namespace units::isq::si;
 
 static_assert(QuantityValue<min_impl<int>>);
 static_assert(QuantityValue<min_impl<double>>);
diff --git a/test/unit_test/static/custom_unit_test.cpp b/test/unit_test/static/custom_unit_test.cpp
index aff34ac1..75ac3a0e 100644
--- a/test/unit_test/static/custom_unit_test.cpp
+++ b/test/unit_test/static/custom_unit_test.cpp
@@ -21,16 +21,16 @@
 // SOFTWARE.
 
 #include "test_tools.h"
-#include <units/physical/si/mass.h>
-#include <units/physical/si/voltage.h>
-#include <units/physical/si/time.h>
-#include <units/physical/si/frequency.h>
+#include <units/isq/si/mass.h>
+#include <units/isq/si/voltage.h>
+#include <units/isq/si/time.h>
+#include <units/isq/si/frequency.h>
 #include <units/math.h>
 
 namespace {
 
 using namespace units;
-using namespace units::physical::si;
+using namespace units::isq::si;
 
 // power spectral density
 struct sq_volt_per_hertz : unit<sq_volt_per_hertz> {};
diff --git a/test/unit_test/static/dimensions_concepts_test.cpp b/test/unit_test/static/dimensions_concepts_test.cpp
index 247df14e..fbde0bfe 100644
--- a/test/unit_test/static/dimensions_concepts_test.cpp
+++ b/test/unit_test/static/dimensions_concepts_test.cpp
@@ -21,12 +21,12 @@
 // SOFTWARE.
 
 
-#include <units/physical/si/si.h>
+#include <units/isq/si/si.h>
 
 namespace {
 
 using namespace units;
-using namespace units::physical;
+using namespace units::isq;
 
 static_assert(Length<si::length<si::metre>>);
 static_assert(!Length<si::time<si::second>>);
diff --git a/test/unit_test/static/fps_test.cpp b/test/unit_test/static/fps_test.cpp
index 5a872a89..60a994e9 100644
--- a/test/unit_test/static/fps_test.cpp
+++ b/test/unit_test/static/fps_test.cpp
@@ -20,22 +20,22 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include <units/physical/si/fps/fps.h>
-#include <units/physical/si/acceleration.h>
-#include <units/physical/si/area.h>
-#include <units/physical/si/energy.h>
-#include <units/physical/si/force.h>
-#include <units/physical/si/length.h>
-#include <units/physical/si/mass.h>
-#include <units/physical/si/power.h>
-#include <units/physical/si/pressure.h>
-#include <units/physical/si/speed.h>
-#include <units/physical/si/time.h>
+#include <units/isq/si/fps/fps.h>
+#include <units/isq/si/acceleration.h>
+#include <units/isq/si/area.h>
+#include <units/isq/si/energy.h>
+#include <units/isq/si/force.h>
+#include <units/isq/si/length.h>
+#include <units/isq/si/mass.h>
+#include <units/isq/si/power.h>
+#include <units/isq/si/pressure.h>
+#include <units/isq/si/speed.h>
+#include <units/isq/si/time.h>
 
 namespace {
 
 using namespace units;
-using namespace units::physical::si::fps;
+using namespace units::isq::si::fps;
 
 /* ************** BASE DIMENSIONS **************** */
 
diff --git a/test/unit_test/static/kind_test.cpp b/test/unit_test/static/kind_test.cpp
index 5821493d..a75927aa 100644
--- a/test/unit_test/static/kind_test.cpp
+++ b/test/unit_test/static/kind_test.cpp
@@ -23,12 +23,12 @@
 #include "test_tools.h"
 #include "units/generic/angle.h"
 #include "units/kind.h"
-#include "units/physical/si/length.h"
-#include "units/physical/si/area.h"
-#include "units/physical/si/speed.h"
+#include "units/isq/si/length.h"
+#include "units/isq/si/area.h"
+#include "units/isq/si/speed.h"
 
 using namespace units;
-using namespace physical::si;
+using namespace isq::si;
 
 namespace {
 
@@ -106,7 +106,7 @@ static_assert(!equivalent<radius, radial_area>);
 static_assert(!equivalent<radius, radial_point>);
 
 
-struct width : kind<width, units::physical::si::dim_length> {};
+struct width : kind<width, units::isq::si::dim_length> {};
 using horizontal_speed = downcast_kind<width, dim_speed>;
 
 struct abscissa : point_kind<abscissa, width> {};                                  // program-defined base point kind
diff --git a/test/unit_test/static/math_test.cpp b/test/unit_test/static/math_test.cpp
index 64cd62f4..cbab7894 100644
--- a/test/unit_test/static/math_test.cpp
+++ b/test/unit_test/static/math_test.cpp
@@ -22,16 +22,16 @@
 
 #include "units/math.h"
 #include "test_tools.h"
-#include "units/physical/si/area.h"
-#include "units/physical/si/volume.h"
-#include "units/physical/si/international/area.h"
-#include "units/physical/si/international/volume.h"
+#include "units/isq/si/area.h"
+#include "units/isq/si/volume.h"
+#include "units/isq/si/international/area.h"
+#include "units/isq/si/international/volume.h"
 
 namespace {
 
 using namespace units;
-using namespace units::physical::si::literals;
-using namespace units::physical::si::international::literals;
+using namespace units::isq::si::literals;
+using namespace units::isq::si::international::literals;
 
 static_assert(compare<decltype(pow<0>(2_q_m)), std::int64_t>);
 static_assert(compare<decltype(pow<1>(2_q_m)), decltype(2_q_m)>);
diff --git a/test/unit_test/static/quantity_kind_test.cpp b/test/unit_test/static/quantity_kind_test.cpp
index b8f96d3d..82ee37e1 100644
--- a/test/unit_test/static/quantity_kind_test.cpp
+++ b/test/unit_test/static/quantity_kind_test.cpp
@@ -22,11 +22,11 @@
 
 #include "test_tools.h"
 #include "units/chrono.h"
-#include "units/physical/si/cgs/speed.h"
-#include "units/physical/si/area.h"
-#include "units/physical/si/frequency.h"
-#include "units/physical/si/speed.h"
-#include "units/physical/si/fps/speed.h"
+#include "units/isq/si/cgs/speed.h"
+#include "units/isq/si/area.h"
+#include "units/isq/si/frequency.h"
+#include "units/isq/si/speed.h"
+#include "units/isq/si/fps/speed.h"
 #include "units/quantity_point.h"
 #include "units/quantity_kind.h"
 #include <cassert>
@@ -36,7 +36,7 @@
 namespace {
 
 using namespace units;
-namespace si = physical::si;
+namespace si = isq::si;
 using namespace si;
 using namespace unit_constants;
 
diff --git a/test/unit_test/static/quantity_point_kind_test.cpp b/test/unit_test/static/quantity_point_kind_test.cpp
index 616c51bf..4b320741 100644
--- a/test/unit_test/static/quantity_point_kind_test.cpp
+++ b/test/unit_test/static/quantity_point_kind_test.cpp
@@ -22,11 +22,11 @@
 
 #include "test_tools.h"
 #include "units/chrono.h"
-#include "units/physical/si/cgs/speed.h"
-#include "units/physical/si/area.h"
-#include "units/physical/si/frequency.h"
-#include "units/physical/si/speed.h"
-#include "units/physical/si/fps/speed.h"
+#include "units/isq/si/cgs/speed.h"
+#include "units/isq/si/area.h"
+#include "units/isq/si/frequency.h"
+#include "units/isq/si/speed.h"
+#include "units/isq/si/fps/speed.h"
 #include "units/quantity_point.h"
 #include "units/quantity_point_kind.h"
 #include <cassert>
@@ -36,7 +36,7 @@
 namespace {
 
 using namespace units;
-namespace si = physical::si;
+namespace si = isq::si;
 using namespace si;
 using namespace unit_constants;
 using sys_seconds = std::chrono::time_point<std::chrono::system_clock, std::chrono::seconds>;
@@ -633,8 +633,8 @@ static_assert(invalid_cast<int>);
 
 namespace mylib {
 
-struct width_kind : kind<width_kind, units::physical::si::dim_length> {};
-struct height_kind : kind<height_kind, units::physical::si::dim_length> {};
+struct width_kind : kind<width_kind, units::isq::si::dim_length> {};
+struct height_kind : kind<height_kind, units::isq::si::dim_length> {};
 struct abscissa_kind : point_kind<abscissa_kind, width_kind> {};
 struct ordinate_kind : point_kind<ordinate_kind, height_kind> {};
 
diff --git a/test/unit_test/static/quantity_point_test.cpp b/test/unit_test/static/quantity_point_test.cpp
index ce2f148a..a597bba9 100644
--- a/test/unit_test/static/quantity_point_test.cpp
+++ b/test/unit_test/static/quantity_point_test.cpp
@@ -24,16 +24,16 @@
 #include "test_tools.h"
 #include "units/chrono.h"
 #include "units/math.h"
-#include "units/physical/si/area.h"
-#include "units/physical/si/speed.h"
-#include "units/physical/si/volume.h"
-#include "units/physical/si/us/length.h"
+#include "units/isq/si/area.h"
+#include "units/isq/si/speed.h"
+#include "units/isq/si/volume.h"
+#include "units/isq/si/us/length.h"
 #include <utility>
 
 namespace {
 
 using namespace units;
-using namespace physical::si;
+using namespace isq::si;
 using namespace unit_constants;
 using namespace std::chrono_literals;
 using sys_seconds = std::chrono::time_point<std::chrono::system_clock, std::chrono::seconds>;
@@ -212,7 +212,7 @@ static_assert(compare<common_quantity_point<quantity_point<dim_length, kilometre
 
 // common_type
 
-using namespace units::physical::si::us::literals;
+using namespace units::isq::si::us::literals;
 
 static_assert(std::equality_comparable<decltype(quantity_point(1_q_m))>);
 static_assert(std::equality_comparable_with<decltype(quantity_point(1_q_m)), decltype(quantity_point(1_q_km))>);
diff --git a/test/unit_test/static/quantity_test.cpp b/test/unit_test/static/quantity_test.cpp
index 287429da..73b0cb80 100644
--- a/test/unit_test/static/quantity_test.cpp
+++ b/test/unit_test/static/quantity_test.cpp
@@ -22,12 +22,12 @@
 
 #include "test_tools.h"
 #include "units/math.h"
-#include "units/physical/si/cgs/speed.h"
-#include "units/physical/si/area.h"
-#include "units/physical/si/frequency.h"
-#include "units/physical/si/speed.h"
-#include "units/physical/si/volume.h"
-#include "units/physical/si/fps/speed.h"
+#include "units/isq/si/cgs/speed.h"
+#include "units/isq/si/area.h"
+#include "units/isq/si/frequency.h"
+#include "units/isq/si/speed.h"
+#include "units/isq/si/volume.h"
+#include "units/isq/si/fps/speed.h"
 #include <chrono>
 #include <complex>
 #include <cstdint>
@@ -38,7 +38,7 @@
 namespace {
 
 using namespace units;
-namespace si = physical::si;
+namespace si = isq::si;
 using namespace si;
 using namespace unit_constants;
 
@@ -202,8 +202,8 @@ static_assert(std::constructible_from<fps::length<fps::foot>, cgs::length<cgs::c
 static_assert(std::convertible_to<cgs::length<cgs::centimetre>, fps::length<fps::foot>>);
 
 // conversion between different dimensions not allowed
-static_assert(!std::constructible_from<length<metre>, physical::si::time<second>>);
-static_assert(!std::convertible_to<physical::si::time<second>, length<metre>>);
+static_assert(!std::constructible_from<length<metre>, isq::si::time<second>>);
+static_assert(!std::convertible_to<isq::si::time<second>, length<metre>>);
 static_assert(!std::constructible_from<length<metre>, speed<metre_per_second>>);
 static_assert(!std::convertible_to<speed<metre_per_second>, length<metre>>);
 
@@ -465,7 +465,7 @@ static_assert(compare<decltype(1_q_m_per_s * 1_q_h), length<scaled_unit<ratio(36
 static_assert(compare<decltype(1_q_m * 1_q_min), quantity<unknown_dimension<exponent<dim_length, 1>, exponent<dim_time, 1>>, scaled_unit<ratio(60), unknown_coherent_unit>, std::int64_t>>);
 static_assert(compare<decltype(1_q_s * 1_q_Hz), dimensionless<one, std::int64_t>>);
 static_assert(compare<decltype(1 / 1_q_min), frequency<scaled_unit<ratio(1, 60), hertz>, std::int64_t>>);
-static_assert(compare<decltype(1 / 1_q_Hz), physical::si::time<second, std::int64_t>>);
+static_assert(compare<decltype(1 / 1_q_Hz), isq::si::time<second, std::int64_t>>);
 static_assert(compare<decltype(1 / 1_q_km), quantity<unknown_dimension<exponent<dim_length, -1>>, scaled_unit<ratio(1, 1, -3), unknown_coherent_unit>, std::int64_t>>);
 static_assert(compare<decltype(1_q_km / 1_q_m), dimensionless<scaled_unit<ratio(1000), one>, std::int64_t>>);
 static_assert(compare<decltype(1_q_m / 1_q_s), speed<metre_per_second, std::int64_t>>);
diff --git a/test/unit_test/static/si_cgs_test.cpp b/test/unit_test/static/si_cgs_test.cpp
index 04dd2f44..f99d4b33 100644
--- a/test/unit_test/static/si_cgs_test.cpp
+++ b/test/unit_test/static/si_cgs_test.cpp
@@ -20,30 +20,30 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include <units/physical/si/acceleration.h>
-#include <units/physical/si/area.h>
-#include <units/physical/si/cgs/acceleration.h>
-#include <units/physical/si/cgs/area.h>
-#include <units/physical/si/cgs/energy.h>
-#include <units/physical/si/cgs/force.h>
-#include <units/physical/si/cgs/length.h>
-#include <units/physical/si/cgs/mass.h>
-#include <units/physical/si/cgs/power.h>
-#include <units/physical/si/cgs/pressure.h>
-#include <units/physical/si/cgs/speed.h>
-#include <units/physical/si/cgs/time.h>
-#include <units/physical/si/energy.h>
-#include <units/physical/si/force.h>
-#include <units/physical/si/length.h>
-#include <units/physical/si/mass.h>
-#include <units/physical/si/power.h>
-#include <units/physical/si/pressure.h>
-#include <units/physical/si/speed.h>
-#include <units/physical/si/time.h>
+#include <units/isq/si/acceleration.h>
+#include <units/isq/si/area.h>
+#include <units/isq/si/cgs/acceleration.h>
+#include <units/isq/si/cgs/area.h>
+#include <units/isq/si/cgs/energy.h>
+#include <units/isq/si/cgs/force.h>
+#include <units/isq/si/cgs/length.h>
+#include <units/isq/si/cgs/mass.h>
+#include <units/isq/si/cgs/power.h>
+#include <units/isq/si/cgs/pressure.h>
+#include <units/isq/si/cgs/speed.h>
+#include <units/isq/si/cgs/time.h>
+#include <units/isq/si/energy.h>
+#include <units/isq/si/force.h>
+#include <units/isq/si/length.h>
+#include <units/isq/si/mass.h>
+#include <units/isq/si/power.h>
+#include <units/isq/si/pressure.h>
+#include <units/isq/si/speed.h>
+#include <units/isq/si/time.h>
 
 namespace {
 
-using namespace units::physical;
+using namespace units::isq;
 
 static_assert(units::detail::quantity_ratio<si::length<si::metre>> == units::ratio(1));
 static_assert(units::detail::quantity_ratio<si::cgs::length<si::cgs::centimetre>> == units::ratio(1, 100));
@@ -65,7 +65,7 @@ static_assert(si::cgs::pressure<si::cgs::barye>(10) == si::pressure<si::pascal>(
 
 namespace si_test {
 
-using namespace units::physical::si::literals;
+using namespace units::isq::si::literals;
 
 static_assert(si::cgs::length<si::cgs::centimetre>(100) == 1_q_m);
 static_assert(si::cgs::mass<si::cgs::gram>(1'000) == 1_q_kg);
@@ -81,7 +81,7 @@ static_assert(si::cgs::pressure<si::cgs::barye>(10) == 1_q_Pa);
 
 namespace cgs_test {
 
-using namespace units::physical::si::cgs::literals;
+using namespace units::isq::si::cgs::literals;
 
 static_assert(100_q_cm == si::length<si::metre>(1));
 static_assert(1'000_q_g == si::mass<si::kilogram>(1));
@@ -97,8 +97,8 @@ static_assert(10_q_Ba == si::pressure<si::pascal>(1));
 
 namespace both_test {
 
-using namespace units::physical::si::literals;
-using namespace units::physical::si::cgs::literals;
+using namespace units::isq::si::literals;
+using namespace units::isq::si::cgs::literals;
 
 // static_assert(100_q_cm == 1_q_m);   // ambiguous
 // static_assert(1'000_q_g == 1_q_kg); // ambiguous
diff --git a/test/unit_test/static/si_fps_test.cpp b/test/unit_test/static/si_fps_test.cpp
index d0c2b387..b4e15570 100644
--- a/test/unit_test/static/si_fps_test.cpp
+++ b/test/unit_test/static/si_fps_test.cpp
@@ -20,30 +20,30 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include <units/physical/si/acceleration.h>
-#include <units/physical/si/area.h>
-#include <units/physical/si/energy.h>
-#include <units/physical/si/force.h>
-#include <units/physical/si/fps/acceleration.h>
-#include <units/physical/si/fps/area.h>
-#include <units/physical/si/fps/energy.h>
-#include <units/physical/si/fps/force.h>
-#include <units/physical/si/fps/length.h>
-#include <units/physical/si/fps/mass.h>
-#include <units/physical/si/fps/power.h>
-#include <units/physical/si/fps/pressure.h>
-#include <units/physical/si/fps/speed.h>
-#include <units/physical/si/fps/time.h>
-#include <units/physical/si/length.h>
-#include <units/physical/si/mass.h>
-#include <units/physical/si/power.h>
-#include <units/physical/si/pressure.h>
-#include <units/physical/si/speed.h>
-#include <units/physical/si/time.h>
+#include <units/isq/si/acceleration.h>
+#include <units/isq/si/area.h>
+#include <units/isq/si/energy.h>
+#include <units/isq/si/force.h>
+#include <units/isq/si/fps/acceleration.h>
+#include <units/isq/si/fps/area.h>
+#include <units/isq/si/fps/energy.h>
+#include <units/isq/si/fps/force.h>
+#include <units/isq/si/fps/length.h>
+#include <units/isq/si/fps/mass.h>
+#include <units/isq/si/fps/power.h>
+#include <units/isq/si/fps/pressure.h>
+#include <units/isq/si/fps/speed.h>
+#include <units/isq/si/fps/time.h>
+#include <units/isq/si/length.h>
+#include <units/isq/si/mass.h>
+#include <units/isq/si/power.h>
+#include <units/isq/si/pressure.h>
+#include <units/isq/si/speed.h>
+#include <units/isq/si/time.h>
 
 namespace {
 
-using namespace units::physical;
+using namespace units::isq;
 
 static_assert(si::fps::length<si::fps::foot>(1) == si::length<si::metre>(0.3048));
 static_assert(si::fps::mass<si::fps::pound>(1) == si::mass<si::kilogram>(0.45359237));
@@ -62,7 +62,7 @@ static_assert(si::fps::pressure<si::fps::poundal_per_foot_sq>(1) > si::pressure<
 
 namespace si_literals {
 
-using namespace units::physical::si::literals;
+using namespace units::isq::si::literals;
 
 static_assert(si::fps::length<si::fps::foot>(1) == 0.3048_q_m);
 static_assert(si::fps::mass<si::fps::pound>(1) == 0.45359237_q_kg);
@@ -82,7 +82,7 @@ static_assert(si::fps::pressure<si::fps::poundal_per_foot_sq>(1) >  1.4881639435
 
 namespace fps_literals {
 
-using namespace units::physical::si::fps::literals;
+using namespace units::isq::si::fps::literals;
 
 static_assert(1_q_ft == si::length<si::metre>(0.3048));
 static_assert(1_q_lb == si::mass<si::kilogram>(0.45359237));
@@ -102,8 +102,8 @@ static_assert(1_q_pdl_per_ft2> si::pressure<si::pascal>(1.4881639435) &&
 
 namespace fps_plus_si_literals {
 
-using namespace units::physical::si::literals;
-using namespace units::physical::si::fps::literals;
+using namespace units::isq::si::literals;
+using namespace units::isq::si::fps::literals;
 
 // static_assert(100_q_cm == 1_q_m);   // ambiguous
 // static_assert(1'000_q_g == 1_q_kg); // ambiguous
@@ -126,7 +126,7 @@ static_assert(1_q_pdl_per_ft2> 1.4881639435_q_Pa &&
 
 namespace fps_test {
 
-using namespace units::physical::si::fps::literals;
+using namespace units::isq::si::fps::literals;
 
 // addition
 
diff --git a/test/unit_test/static/si_test.cpp b/test/unit_test/static/si_test.cpp
index 4966ee36..6f313992 100644
--- a/test/unit_test/static/si_test.cpp
+++ b/test/unit_test/static/si_test.cpp
@@ -22,12 +22,12 @@
 
 #include "test_tools.h"
 #include <units/math.h>
-#include <units/physical/si/si.h>
+#include <units/isq/si/si.h>
 
 namespace {
 
 using namespace units;
-using namespace units::physical::si;
+using namespace units::isq::si;
 
 /* ************** BASE DIMENSIONS **************** */
 
diff --git a/test/unit_test/static/unit_constants.cpp b/test/unit_test/static/unit_constants.cpp
index 7d4bd2f6..b940f965 100644
--- a/test/unit_test/static/unit_constants.cpp
+++ b/test/unit_test/static/unit_constants.cpp
@@ -21,13 +21,13 @@
 // SOFTWARE.
 
 #include "units/bits/external/hacks.h"
-#include "units/physical/dimensions/length.h"
-#include "units/physical/dimensions/speed.h"
-#include "units/physical/si/length.h"
-#include "units/physical/si/mass.h"
-#include "units/physical/si/time.h"
-#include "units/physical/si/area.h"
-#include "units/physical/si/speed.h"
+#include "units/isq/dimensions/length.h"
+#include "units/isq/dimensions/speed.h"
+#include "units/isq/si/length.h"
+#include "units/isq/si/mass.h"
+#include "units/isq/si/time.h"
+#include "units/isq/si/area.h"
+#include "units/isq/si/speed.h"
 #include <cassert>
 #include <cstdint>
 #include <type_traits>
@@ -37,9 +37,9 @@
 #endif
 
 using namespace units;
-using namespace units::physical;
-using namespace units::physical::si;
-using namespace units::physical::si::unit_constants;
+using namespace units::isq;
+using namespace units::isq::si;
+using namespace units::isq::si::unit_constants;
 
 static_assert(2 * m == 2_q_m);
 static_assert(2 * s == 2_q_s);
diff --git a/test/unit_test/static/unit_test.cpp b/test/unit_test/static/unit_test.cpp
index f02086a9..28823f70 100644
--- a/test/unit_test/static/unit_test.cpp
+++ b/test/unit_test/static/unit_test.cpp
@@ -23,12 +23,12 @@
 #include "test_tools.h"
 #include "units/unit.h"
 #include "units/bits/equivalent.h"
-#include "units/physical/si/prefixes.h"
+#include "units/isq/si/prefixes.h"
 
 namespace {
 
 using namespace units;
-using namespace units::physical;
+using namespace units::isq;
 
 struct metre : named_unit<metre, "m", si::prefix> {};
 struct centimetre : prefixed_unit<centimetre, si::centi, metre> {};
diff --git a/test/unit_test/static/us_test.cpp b/test/unit_test/static/us_test.cpp
index e66bb45f..07ef18a5 100644
--- a/test/unit_test/static/us_test.cpp
+++ b/test/unit_test/static/us_test.cpp
@@ -20,15 +20,15 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include <units/physical/si/speed.h>
-#include <units/physical/si/international/speed.h>
+#include <units/isq/si/speed.h>
+#include <units/isq/si/international/speed.h>
 #include <utility>
 
 namespace {
 
 using namespace units;
-using namespace units::physical::si;
-using namespace units::physical::si::international;
+using namespace units::isq::si;
+using namespace units::isq::si::international;
 
 /* ************** BASE DIMENSIONS **************** */
 
diff --git a/test_package/test_package.cpp b/test_package/test_package.cpp
index 997e0d45..d2120c84 100644
--- a/test_package/test_package.cpp
+++ b/test_package/test_package.cpp
@@ -20,13 +20,13 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include <units/physical/si/speed.h>
+#include <units/isq/si/speed.h>
 #include <units/quantity_io.h>
 #include <iostream>
 
 using namespace units;
 
-template<physical::Length Length, physical::Time Time>
+template<isq::Length Length, isq::Time Time>
 constexpr auto avg_speed(Length d, Time t)
 {
   return d / t;
@@ -34,6 +34,6 @@ constexpr auto avg_speed(Length d, Time t)
 
 int main()
 {
-  using namespace units::physical::si::literals;
+  using namespace units::isq::si::literals;
   std::cout << "Average speed = " << avg_speed(240._q_km, 2_q_h) << '\n';
 }