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.

or Système International d'Unités or SI system

International decimal system of weights and measures derived from and extending the metric system of units. Adopted by the 11th General Conference on Weights and Measures in 1960, it was developed to eliminate overlapping but different systems of units of measures fostered by rapid advances in science and technology in the 19th–20th centuries. Its fundamental units include the metre (m) for length, the kilogram (kg) for mass, and the second (sec) for time. Derived units include those for force (newton, N), energy (joule, J), and power (watt, W).

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