International System of Units
The International System of Units, abbreviated SI (for the French name Système International d'Unités), is the most widely used system of units in science. It can legally be used in every country in the world (including the United States), 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 and is built on the seven SI base units, which are used to define various SI derived units.
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 spelt 'gramme', though that is an older spelling.
See also:
- SI base units and SI derived units
- SI supplementary units
- SI prefixes
- Standards and Units
- Conversion of units
- metrology
- UTC (Coordinated Universal Time)
- Orders of magnitude
External links and references:
- http://www.bipm.fr/enus/3_SI/base_units.html
- I. Mills, Tomislav Cvitas, Klaus Homann, Nikola Kallay, IUPAC: Quantities, Units and Symbols in Physical Chemistry, 2nd ed., Blackwell Science Inc 1993, ISBN 0632035838.
Also, Sports Illustrated magazine.