| discretionary(adjective, open, free, voluntary, elective) |
| nonmandatory |
| optional(adjective, possible, voluntary, elective, electoral) |
| elective(adjective, open, free, able, voluntary) |
| facultative(adjective, open, free, voluntary, elective) |
| voluntary(adjective, open, free, elective, electoral) |
| arbitrary(adjective, open, free, voluntary, elective) |
| discretional(adjective, open, free, voluntary, elective) |
| electoral |
| possible(adjective, voluntary, elective) |
| alternative(open, free, voluntary, elective) |
| constituent(adjective, electoral) |
| eligible |
| extra(open, free, voluntary, elective) |
| free(open, voluntary, elective) |
| no strings attached(expression, idiom, open, free, voluntary) |
| noncompulsory(open, free, voluntary, elective) |
| not compulsory(expression, adjective, electoral) |
| not obligatory(expression, idiom) |
| not required(expression, open, free, voluntary, elective) |