The twelfth Greek letter, and the SI prefix for one millionth.
Also known as: Greek letter mu, Mu symbol, Micro symbol, Micron sign, μ
Mu is the only Greek letter in this batch with a formally standardised meaning: as an SI prefix it means one millionth, as in the microgram and the micrometre. Everywhere else it is an ordinary variable name.
Is a letter of the Greek alphabet before it is a symbol: what it denotes is fixed by the field it appears in, not by the character itself. The uses below are the documented conventions, not competing definitions.
Contexts: Mathematics
In the SI system, denotes the prefix micro-, meaning one millionth — µg, µm, µs.
Contexts: Mathematics
In statistics, denotes the mean of a population, as against the sample mean.
Contexts: Mathematics
In mechanics, denotes the coefficient of friction between two surfaces.
Contexts: Mathematics
In electromagnetism, denotes magnetic permeability.
Contexts: Mathematics
In particle physics, denotes the muon, a heavier relative of the electron.
Contexts: Mathematics
Has a formally defined meaning as an SI prefix, which none of the other letters in this batch does — micro- is fixed by the International System of Units rather than by convention.
The SI defines the prefix, not the letter. Outside a unit, mu is an ordinary variable like any other.
Contexts: Mathematics
Exists in Unicode twice over: as the Greek letter and as a separate micro sign kept for compatibility with older encodings, which look alike but are distinct characters.
A practical trap for anyone searching or sorting text: two visually identical characters that do not match each other.
Contexts: Mathematics
A rounded u shape whose left stroke descends well below the writing line before ending.
The SI prefix micro has its own character, U+00B5, separate from this Greek letter at U+03BC. They render almost identically and are substituted for each other constantly.
Population mean and population standard deviation are the paired parameters of a normal distribution.