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SI

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Alternate use: SI is also the ISO country code for Slovenia

The International System of Units, abbreviated SI (for the French phrase Système International d'Unités), is the most widely used system of units. Along with the older cgs (centimetre, gram, second) system, SI is sometimes referred to as the metric system (especially in the United States, which has not widely adopted its use in everyday commerce, and the UK where conversion is incomplete).

SI is built on seven SI base units, such as the kilogram and metre. These are used to define various SI derived units. SI also defines a number of SI prefixes to be used with the units: these combine with any unit name to give subdivisions and multiples. For example, the prefix kilo denotes a multiple of a thousand, so the kilometre is 1,000 metres, the kilogram 1,000 grams and so on.

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SI writing style

The system can legally be used in every country in the world, and in many countries its use is obligatory. Those countries that still give official recognition to non-SI units (e.g. US, UK) define them in terms of SI units. It was adopted by the 11th General Conference on Weights and Measures (CGPM) in 1960. (See weights and measures for a history of the development of units of measurement).

Notes

Americans frequently spell 'metre' as 'meter', and 'litre' as 'liter'; however 'metre' and 'litre' are the official BIPM names for these units, although the American usage has been approved by the US government. The official US spelling for 'deca' is 'deka', though Americans use the international spelling more often than the American one.

The unit 'gram' is also sometimes spelled 'gramme' in English speaking countries, though that is an older spelling. Several other languages use the American spelling. In written practice only the abbreviated (prefixed) symbols are used, qualifying the spelling issue.

The English language version of the official SI brochure (http://www.bipm.org/pdf/si-brochure.pdf) published by the BIPM uses the decimal point instead of the comma to separate the integer portion of a number from the fractional portion. This indicates that the use of the comma is not an inherent part of SI, but a part of the language and culture in which it is used in a particular case. In the U.S., the decimal point should be used.

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External links

wikipedia.org dumped 2003-03-17 with terodump