International System of Units, officially called the Système International d'Unités, or SI, system of units adopted by the 11th General Conference on Weights and Measures (1960). It is based on the metric system. The basic units of length, mass, and time are those of the mks system of metric units: the meter, kilogram, and second. Other basic units are the ampere of electric current, the kelvin of temperature (a degree of temperature measured on the Kelvin temperature scale), the candela, or candle, of luminous intensity, and the mole, used to measure the amount of a substance present. All other units are derived from these basic units.
See U.S. National Bureau of Standards, Spec. Pub. 330, International System of Units (1971).