Micro-

Look up micro- in Wiktionary, the free dictionary.

Micro (Greek letter μ, mu, non-italic) 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".

It is the only SI prefix which uses a character not from the Latin alphabet. In Unicode, the symbol is represented by U+03BC μ GREEK SMALL LETTER MU or the legacy symbol U+00B5 µ MICRO SIGN. The prefix "mc" is commonly used in healthcare or when the character "μ" is not available; for example, "mcg" commonly denotes a microgram.^[2] The letter "u" is sometimes used instead of "μ" when non-Latin characters are not available.