Metric system unit prefix / From Wikipedia, the free encyclopedia

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Micro (Greek letter μ (U+03BC) or the legacy symbol µ (U+00B5)) is a unit prefix in the metric system denoting a factor of 10−6 (one millionth).[1] Confirmed in 1960, the prefix comes from the Greek μικρός (mikrós), meaning "small".

The symbol for the prefix is the Greek letter μ (mu). It is the only SI prefix which uses a character not from the Latin alphabet. "mc" is commonly used as a prefix when the character "μ" is not available; for example, "mcg" commonly denotes a microgram.[2] This may be ambiguous in rare circumstances in that mcg could also be read as a micrigram, i.e. 10−14 g; however the prefix micri is not standard, nor widely known, and is considered obsolete. The letter u, instead of μ, was allowed by an ISO document,[3] but that document has been withdrawn in 2001, however DIN 66030:2002 still allows this substitution.[4]