International System of Units

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 technological 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 ( e.g., force, power, frequency) are stated in terms of the basic units ( e.g., 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). Those involving a multiple of 103 are recommended; compounds of these are not recommended ( e.g., for n). [Fr. Système International d'Unités]

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In·ter·na·tion·al System of Units .int-ər-'nash-nəl-, -ənəl- n an internationally accepted system of units based on the metric system and having the meter, kilogram, second, ampere, kelvin, mole, and candela as base units, the radian and steradian as supplementary units, and deriving all other units from these abbr. SI called also International System

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see SI unit, under unit.

Medical dictionary. 2011.

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  • International System of Units (SI) — ▪ Table International System of Units (SI) Base units unit abbreviation physical quantity metre m length second s time kilogram kg mass ampere A electric current kelvin K thermodynamic temperature candela cd luminous intensity mole mol amount of… …   Universalium

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  • International System of Units — noun a complete metric system of units of measurement for scientists; fundamental quantities are length (meter) and mass (kilogram) and time (second) and electric current (ampere) and temperature (kelvin) and amount of matter (mole) and luminous… …   Useful english dictionary

  • International System of Units — noun Date: 1932 a system of units based on the metric system and developed and refined by international convention especially for scientific work abbreviation SI …   New Collegiate Dictionary

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