# Mu

<*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 denotes the least value of x for which E = x, i.e. the least fixed point of the function \ x . E. The recursive 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)See fixed point combinator.

3. <*database*> multiple value.