# Système International d'Unités

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Related to Système International d'Unités: SI units, International System of Units

## In·ter·na·tion·al Sys·tem of U·nits (SI),

, Système International d'Unités (in'tĕr-na'shŭn-ăl sis'tem yū'nits, sēs-tĕm' ahn-tĕr-nahs-ē'ōn-nahl' dūn'nē-tā'),
A system of measurements, based on the metric system, adopted at the 11th General Conference on Weights and Measures of the International Organization for Standardization (1960) to cover both the coherent units (basic, supplementary, and derived units) and the decimal multiples and submultiples of these units formed by use of prefixes proposed for general international scientific and technologic use. SI proposes seven basic units: meter (m), kilogram (kg), second (s), ampere (A), kelvin (K), candela (cd), and mole (mol) for the basic quantities of length, mass, time, electric current, temperature, luminous intensity, and amount of substance, respectively; supplementary units proposed include the radian (rad) for plane angle and steradian (sr) for solid angle; derived units (for example, force, power, frequency) are stated in terms of the basic units (for example, velocity is in meters per second, m s-1). Multiples (prefixes) in descending order are: exa- (E, 1018), peta- (P, 1015), tera- (T, 1012), giga- (G, 109), mega- (M, 106), kilo- (k, 103), hecto- (h, 102), deca- (da, 101), deci- (d, 10-1), centi- (c, 10-2), milli- (m, 10-3), micro- (μ, 10-6), nano- (n, 10-9), pico- (p, 10-12), femto- (f, 10-15), atto- (a, 10-18). Proposed prefixes are zetta- (Z, 1021), yotta- (Y, 1024), zepto- (z, 10-21), and yocto- (y, 10-24).
[Fr. Système International d'Unités]

## International System of Units

; Système International d'Unités; SI units system of weights and measures, e.g. metre (m; length); kilogram (kg; mass); litre (L; volume); second (s; time); ampere (A; electric current); kelvin (K; temperature); pascal (Pa; pressure); mole (mol; amount of substance); derived units (e.g. force, power, frequency) are stated in terms of the basic units; multiples of units are termed, in descending order: tera- (T; 1012), giga- (G; 109), mega- (M, 106), kilo- (K; 103), hecto- (h; 102), deca (da; 101), deci- (d; 10-1), centi- (c, 10-2), milli- (m, 10-3), micro- (µ, 10-6), nano- (n, 10-9)

## Système International d'Unités

the International System of Units; introduced in 1977, a universally accepted system of units of measure and providing units for the health professions; abbreviated SI. See Table 3.
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