An<unk>  (also known as a metric<unk>  is a name or associated symbol that precedes a unit of measure (or its symbol) to form a decimal multiple or submultiple.  The abbreviation<unk>  is from the French language name Système International d’Unités (also known as International System of Units). <unk> es are used to reduce the quantity of zeroes in numerical equivalencies.  For example, one-billionth of an ampere (a small electrical current) can be written as 0.000 000 001 ampere. In symbol form, this is written as 0.000 000 001 A.  Using an<unk> , these are equivalent to 1 nanoampere or 1 nA. The<unk> es are governed by the Bureau International des Poids et Mesures (BIPM, also known as the International Bureau of Weights and Measures) and are the product of four resolutions dating from 1960 to 1991.
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