Many scientists have been recognized with the assignment of their names as international units by the International Committee for Weights and Measures or as non-SI units. The International System of Units (abbreviated SI from French: Système international d'unités) is the most widely used system of units of measurement. There are 7 base units and 22 derived units[1] (excluding compound units). These units are used both in science and in commerce. Two of the base SI units and 17 of the derived units are named after scientists.[2] 28 non-SI units are named after scientists. By this convention, their names are immortalised. As a rule, the SI units are written in lowercase letters, but symbols of units derived from the name of a person begin with a capital letter.