[pur-myoo-tey-shuh n] /ˌpɜr myʊˈteɪ ʃən/
the act of permuting or permutating; alteration; transformation.
a combination of items made by reordering
an alteration; transformation
a fixed combination for selections of results on football pools Usually shortened to perm
mid-14c., from Old French permutacion “change, shift” (14c.), from Latin permutationem (nominative permutatio) “a change, alteration, revolution,” noun of action from past participle stem of permutare “change thoroughly, exchange,” from per- “thoroughly” (see per) + mutare “to change” (see mutable).
1. An ordering of a certain number of elements of a given set.
For instance, the permutations of (1,2,3) are (1,2,3) (2,3,1) (3,1,2) (3,2,1) (1,3,2) (2,1,3).
Permutations form one of the canonical examples of a “group” – they can be composed and you can find an inverse permutation that reverses the action of any given permutation.
The number of permutations of r things taken from a set of n is
n P r = n! / (n-r)!
where “n P r” is usually written with n and r as subscripts and n! is the factorial of n.
What the football pools call a “permutation” is not a permutation but a combination – the order does not matter.
2. A bijection for which the domain and range are the same set and so
f(f'(x)) = f'(f(x)) = x.
noun 1. a mathematical group whose elements are permutations and in which the product of two permutations is the same permutation as is obtained by performing them in succession.
[pur-kee] /ˈpɜr ki/ adjective, perkier, perkiest. 1. jaunty; cheerful; brisk; pert. /ˈpɜːkɪ/ adjective perkier, perkiest 1. jaunty; lively 2. confident; spirited adj. 1820, from perk (v.) + -y (2). Of young women’s breasts since at least 1937. Related: Perkily; perkiness. adjective Energetic and jaunty; lively; chipper (1855+)
- Pernicious anaemia
noun 1. a form of anaemia characterized by lesions of the spinal cord, weakness, sore tongue, numbness in the arms and legs, diarrhoea, etc: associated with inadequate absorption of vitamin B12
[per-nish-uh s] /pərˈnɪʃ əs/ adjective 1. causing insidious harm or ruin; ruinous; injurious; hurtful: pernicious teachings; a pernicious lie. 2. deadly; fatal: a pernicious disease. 3. Obsolete. evil; wicked. /pəˈnɪʃəs/ adjective 1. wicked or malicious: pernicious lies 2. causing grave harm; deadly adj. early 15c., from Middle French pernicios (13c., Modern French pernicieux) and directly […]