a decimal system of weights and measures, adopted first in France but now widespread, universally used in science, mandatory for use for all purposes in a large number of countries, and favored for use in most (as in the U.S.). The basic units are the meter (39.37 inches) for length and the gram (15.432 grains) for mass or weight. Derived units are the liter (0.908 U.S. dry quart, or 1.0567 U.S. liquid quart) for capacity, being the volume of 1000 grams of water under specified conditions; the are (119.6 square yards) for area, being the area of a square 10 meters on a side; and the stere (35.315 cubic feet) for volume, being the volume of a cube 1 meter on a side, the term "stere," however, usually being used only in measuring firewood.
Names for units larger and smaller than these are formed from the above names by the use of the following prefixes: kilo-, 1000; hecto-, 100; deka-, 10; deci-, 0.1; centi-, 0.01; milli-, 0.001. To these are often added: tera-, one trillion; giga-, one billion; mega-, one million. With the addition of basic physical units it is now officially known by the French name Le Système International d'Unités (abbreviation SI ) or in English as the International System of Units.
[ 1860-65 ]