The Study of Physics involves a lot of measurements.

 In 1975 Scientists agreed on a system known as the International System of Units (Systeme’ Internationale).

The SI, or metric system of units is the internationally accepted system of units for measurement in all of the sciences, including physics.

The SI consists of base units and derived units:
(1) The set of Base units comprises an irreducible set of units for measuring all physical variables.

These quantities cannot be obtained from any other physical quantities.

(2) The Derived units can be expressed in terms of the base units.