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A lower-case Greek mu with a straight descender, used as the SI prefix for one millionth.
Also known as: Micro, u
µ is the SI prefix micro, meaning one millionth. It has its own character, U+00B5 MICRO SIGN, distinct from the Greek letter mu it is drawn from — a distinction that matters for searching and sorting text.
Denotes the SI prefix micro, a factor of one millionth, written before a unit symbol with no space: µm, µs, µF.
Contexts: Mathematics
Is encoded as U+00B5 MICRO SIGN, a separate character from U+03BC GREEK SMALL LETTER MU, which the two look alike enough to be substituted for each other in practice.
Contexts: Software
Is often replaced by a plain letter u where the character cannot be typed — uF on a capacitor marking, ug in a dosage — a substitution the SI does not sanction but which is widespread.
Contexts: Electrical equipment
A lower-case u shape whose left-hand stroke continues straight down below the writing line, giving a rounded body with one descending leg.
The micro sign and the Greek letter mu are different characters that render almost identically.