Permanent

Used in English since 15th century, from Middle French permanent, from Latin permanens, from permanÄ“o ("I stay to the end").

Full definition of permanent

Without end, eternal.Nothing in this world is truly permanent.
Lasting for an indefinitely long time.The countries are now locked in a permanent state of conflict.

(plural permanents)

A chemical hair treatment imparting or removing curliness, whose effects typically last for a period of weeks; a perm.

1943, Raymond Chandler, The High Window, Penguin 2005, p. 8:She had pewter-coloured hair set in a ruthless permanent, a hard beak and large moist eyes with the sympathetic expression of wet stones.

n \times n matrix

a_{ij} \,

, the sum over all permutations

\pi \,

\prod_{i=1}^n{a_{i\pi(i)}