A complete set of units which is used for measuring all kinds of fundamental and derived quantities is called a system of units.
(i) The CGS or the metric system: In this system the fundamental units of length, mass and time are centimeter, gram and second respectively.
(ii) The FPS or the British system: In this system the fundamental units of length, mass and time are foot, pound and second respectively.
(iii) The MKS system: In this system the fundamental units of length, mass and time are metre, kilogram and second respectively.
(iv) The SI: SI is the system of abbreviation for System Internationaled’ Unites, which is the French equivalent for international system of units. In this system the fundamental units of length, mass, time, electric current temperature, luminous intensity and amount of substance are metre, kilogram, second, ampere, Kelvin, candela and mole respectively.
