permutation
     n 1: an event in which one thing is substituted for another; "the
          replacement of lost blood by a transfusion of donor
          blood" [syn: {substitution}, {transposition}, {replacement},
           {switch}]
     2: the act of changing the arrangement of a given number of
        elements
     3: complete change in character or condition; "the
        permutations...taking place in the physical world"- Henry
        Miller
     4: act of changing the lineal order of objects in a group
Source: WordNet® 2.0