Nouns

(n)substitution, permutation, transposition, replacement, switchan event in which one thing is substituted for another“the replacement of lost blood by a transfusion of donor blood”
(n)permutationthe act of changing the arrangement of a given number of elements
(n)permutationcomplete change in character or condition“the permutations … taking place in the physical world” (Henry Miller)
(n)permutationact of changing the lineal order of objects in a group