permutation
Concise Oxford English Dictionary © 2008 Oxford University Press:
permutation/pɜːmjuˈteɪʃn/
▶noun each of several possible ways in which a set or number of things can be ordered or arranged.
■ Mathematics the action of changing the arrangement of a set of items.
■ Brit. a selection of a specified number of matches in a football pool.
– derivatives
permutational adjective.
permutational adjective.
– origin ME (in the sense ‘exchange, barter’): via OFr. from L. permutatio(n-), from permutare (see permute).
'permutation' also found in these Oxford entries:

