# SI units

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Related to SI units: Metric units

## SI units

An internationally agreed system of coherent metric units, increasingly used for all scientific and technical purposes. It was developed from the MKS system of units and replaces the CGS and Imperial systems of units. There are seven base units that are arbitrarily defined and dimensionally independent (see Table 1). These include the kelvin and the second. The meter has been redefined but is still a base unit. The base units can be combined by multiplication and/or division to derive other units, such as the watt or the newton (see Table 2). A set of prefixes, including kilo- and micro-, can be used to form decimal multiples or submultiples of the units (see Table 3). Any physical quantity may then be expressed in terms of a number multiplied by the appropriate SI unit for that quantity.## International System of Units (SI)

A system of units based on the following fundamental quantities: metre, kilogram, second, ampere, kelvin, candela, and mole.

## SI units

(**S**ystème

**I**nternational d'Unites; International System of Units) A system of standard units of measurement finalized at the 14th General Conference on Weights and Measures in 1971. It is based on seven units of measure, including three from the MKS system (meter-kilogram-second), the ampere for electrical current, the Kelvin for temperature, the candela for luminosity and the mole for molecular weight. See MKS system, amp, Kelvin, candela and mole.

BASIC SI UNITSQuantity Unit of Measurementlength (l) meter (m) mass (m) kilogram (kg) time (t) second (s) current (I) ampere (A) temperature kelvin (K) atomic weight mole (mol) luminosity candela (cd)DERIVED SI UNITSQuantity Unit of Measurementforce (f) newton (N) work (W) joule (J) power (P) watt (W) pressure (P) pascal (pa) frequency (f) Hertz (Hz) electric charge (Q) coulomb (C) potential (V) volt (V) capacitance (C) Farad (F) resistance (R) ohm

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