Having the power or authority to elect; electoral.
Determined by independent arbiter.
Done intentionally, not by accident
Empty or unoccupied:
Employing or exerting compulsion; coercive.
Existing outside traditional or established institutions or systems:
(Philos.) Not subject to determinism; free
Capable of existing under varying environmental conditions or by assuming various behaviors. Bacteria that are facultative aerobes can live in both aerobic and anaerobic environments. A facultative parasite can live independently of its usual host.
Due to necessity or emergency
Done or undertaken of one's own free will:
Acting from necessity or compulsion; involuntary.
Of, relating to, or giving advantage or preference:
Find another word for optional. In this page you can discover 37 synonyms, antonyms, idiomatic expressions, and related words for optional, like: elective, arbitrary, volitional, not required, noncompulsory, free, unrestricted, unforced, with no strings attached, take-it-or-leave-it and compulsory.