| voluntary(adjective, free, deliberate, natural, choice) |
| discretionary(adjective, open, chance, choice, will) |
| elective(adjective, choice, able, possible, voluntary) |
| free(adjective, deliberate, natural, willing, will) |
| discretional(adjective, free, deliberate, natural, choice) |
| unforced(adjective, free, deliberate, natural, willing) |
| alternative(adjective, irregular, extra, different, possible) |
| arbitrary(adjective, chance, possible, uninformed, random) |
| volitional(adjective, free, deliberate, natural, willing) |
| facultative(adjective, choice, possible, voluntary, elective) |
| uncalled-for(adjective, extra, unwarranted, unnecessary, pointless) |
| unnecessary(adjective, extraordinary, new, spare, fresh) |
| nonobligatory(adjective, possible, voluntary, elective) |
| open(adjective, possible, voluntary, elective) |
| spontaneous(adjective, free, deliberate, natural, willing) |
| volunteer(adjective, free, deliberate, natural, willing) |
| willful(adjective, free, deliberate, natural, unreasonable) |
| extra(adjective, spare, excess, further, surplus) |
| nonmandatory |
| uncoerced |