WordNet sense 1 (one of a number of things from which only one can be chosen):

choice, option

WordNet sense 2 (allowing a choice):

alternate, alternate

WordNet sense 3 (being of second rank or importance or value; not direct or immediate):

secondary

WordNet sense 4 (not conventional or conformist):

unconventional

WordNet sense 5 (necessitating a choice between mutually exclusive possibilities):

mutually exclusive

WordNet sense 6 (serving or tending to divide or separate):

disjunctive