character (Greek letter).
1. unit /micro/ prefix denoting division by 10^6, e.g. mu m
(micrometre, a millionth part of a metre). Sometimes written
as a 'u', the ASCII character nearest in appearance.
2. mathematics /myoo/ In the theory of functions, mu x . E
function mu f . H f satisfies (and is defined by) the equation
mu f . H f = H (mu f . H f)
An alternative notation for the same function is
fix H = H (fix H)
(1995-10-30)