THE INTERNATIONAL SYSTEM (SI)
 

The International System is often abbreviated SI, which stands for Système International in French. This scheme in its earlier form, mks, has existed since the 1800s, but more recently it has been defined in a rigorous fashion by the General Conference on Weights and Measures.
The base units in SI quantify displacement, mass, time, temperature, electric current, brightness of light, and amount of matter (in terms of the number of atoms or molecules in a sample). Respectively, the units in SI are known as the meter, the kilogram, the second, the kelvin (or degree kelvin), the ampere, the candela, and the mole.We’ll define these in detail shortly.