SI
(Système International, International System of Units)

is a metric-based system of weights and measures adopted in 1960 by the 11th General Conference on Weights and Measures, in which 36 countries, including the U.S., participated. SI consists of seven base units:

There are two supplemental units:

Unit Quantity meter (m) length kilogram (kg) mass second (s) time ampere (A) electric current Kelvin (K) thermodynamic temperature mole (mol) amount of substance candela (cd) luminous intensity There are two supplemental units:

Unit	Quantity
radian (rad)	plane angle
steradian (sr)	solid angle

There are many derived units, each defined in terms of the base units: for example, the newton (N) — a unit of force — is defined by the formula kg x m/s2, and the joule (J), by the relationship N x m.

Also see metric system.