The metric system is an international decimalised system of measurement, first adopted by France in 1791, that is the common system of measuring units usedby most of the world. It exists in several variations, with different choices of fundamental units, though the choice of base units does not affect its day-to-day use. Over the last two centuries,different variants have been considered the metric system. Since the 1960s the International System of Units ("Système International d'Unités" in French, hence "SI") has been the internationallyrecognised standard metric system. Metric units are widely used around the world for personal, commercial and scientific purposes. A standard set of prefixes in powers of ten may be used to derive larger andsmaller units from the base units.
According to the US CIA World Factbook in 2006, the International System of Units is the official system of measurement for all nations except for Burma, Liberia,and the United States.
The idea of a metric system has been attributed to John Wilkins, first secretary of the Royal Society of London in 1668. The idea did not catch on, and Englandcontinued with its existing system of various weights and measures.
In 1670, Gabriel Mouton, a French abbot and scientist, proposed a decimal system of measurement based on the circumference of the Earth.His suggestion was a unit, milliare, that was defined as a minute of arc along a meridian. He then suggested a system of sub-units, dividing successively by factors of ten into the centuria, decuria,virga, virgula, decima, centesima, and millesima.
All derived units would use a common set of prefixes for each multiple. Thus the prefix kilo could be used for mass (kilogram) or length(kilometre) both indicating a thousand times the base unit. This did not prevent the popular use of names for some derived units such as the tonne which is a megagram; derived from old customary...