Synonyms for Optional:

• adj.

  •all (adjective)
  • optional.
  •arbitrary (adjective)
  • in judicious,
  • wayward,
  • injudicious,
  • un accountable,
  • in-judicious,
  • un-accountable,
  • in-consistent,
  • offhand,
  • un-reasonable,
  • un scientific,
  • in consistent,
  • un-scientific,
  • un reasonable.
  •discretionary (adjective)
  • nonobligatory,
  • non obligatory,
  • un restricted,
  • most nonobligatory,
  • non mandatory,
  • more nonmandatory,
  • most nonmandatory,
  • un-restricted,
  • more nonobligatory,
  • nonmandatory,
  • non-obligatory,
  • judge jury.
  •elective (adjective)
  • more voting,
  • most voting.
  •extra (adjective)
  • graviest,
  • more gingerbread,
  • ICER,
  • icest,
  • surplus,
  • sur plusser,
  • tipper,
  • sur-plusser,
  • most button,
  • fussest,
  • most another,
  • gravy,
  • un used,
  • re serve,
  • tippest,
  • more button,
  • most lagniappe,
  • supplementary,
  • most beyond,
  • re-serve,
  • in addition,
  • more another,
  • be-yond,
  • most gingerbread,
  • more reserve,
  • over above,
  • gravier,
  • sur plussest,
  • in reserve,
  • more lagniappe,
  • more beyond,
  • extra-ordinary,
  • perkest,
  • be yond,
  • un-used,
  • sur-plussest,
  • most reserve,
  • super-numerary,
  • super numerary.
  •inessential (adjective)
  • in essential,
  • in-essential.
  •uncalled-for (adjective)
  • uncalled for,
  • Non-essential,
  • unwelcome.
  •uncompelled (adjective)
  • un compelled,
  • un-compelled.
  •unessential (adjective)
  • un-essential,
  • un-important,
  • un essential.
  •unforced (adjective)
  • un forced,
  • un-forced.
  •unnecessary (adjective)
  • uncritical,
  • causeless,
  • supererogatory.
  •unneeded (adjective)
  • un needed,
  • un-needed.
  •unrequired (adjective)
  • un required,
  • un-required.
  •voluntary (adjective)
  • more freewilled,
  • in-tended,
  • more unbidden,
  • more free willed,
  • more unprescribed,
  • most unbidden,
  • most unprescribed,
  • more discretional,
  • de liberate,
  • most witting,
  • most freewilled,
  • most wished,
  • free willed,
  • un constrained,
  • more wished,
  • more willed,
  • most designful,
  • in-dependent,
  • more witting,
  • in dependent,
  • un asked,
  • most discretional,
  • un prescribed,
  • un-prescribed,
  • un-asked,
  • most volunteer,
  • un-paid,
  • most willed,
  • un-bidden,
  • unpaid,
  • more opted,
  • most free willed,
  • most free-willed,
  • un paid,
  • more free-willed,
  • more designful,
  • most opted,
  • more volunteer,
  • in tended,
  • un bidden,
  • de-liberate.

• n.

  •
  • going,
  • usable,
  • available,
  • public,
  • vacant,
  • accessible,
  • on offer,
  • spare,
  • seasonal.
  •
  • choice.
  •discretionary (noun)
  • unrestricted,
  • volitional,
  • take it or leave it,
  • free,
  • with no strings attached,
  • noncompulsory,
  • not required.
  •ex gratia (noun)
  • ex gratia.

• Other synonyms:

  •
  • open-ended.
  •Other relevant words:
  • optionally,
  • selective,
  • extramural,
  • option,
  • uncoerced,
  • any,
  • autonomous,
  • spontaneous,
  • self-acting,
  • alternative,
  • intentional,
  • Offered,
  • deliberate,
  • gratuitous,
  • uninvited,
  • unessential,
  • Self-determining,
  • volunteer,
  • premeditated,
  • unsought,
  • Unbesought,
  • unrequested,
  • unprompted,
  • freewill,
  • intended,
  • independent,
  • unrequired,
  • inessential,
  • wilful,
  • Proffered,
  • self-determined,
  • additional,
  • planned,
  • unneeded,
  • uncalled-for,
  • unasked,
  • Willed,
  • willful,
  • electives,
  • free will,
  • unpressured,
  • Volitient,
  • Self-active,
  • permissive,
  • uninfluenced,
  • no strings attached,
  • up to the individual,
  • unconstrained,
  • disjunctive,
  • Volitive,
  • secondary,
  • unsolicited,
  • extracurricular,
  • external,
  • non-compulsory.

Paraphrases for Optional:

• Equivalence

  • Adjective
    facultative.
  • Noun, singular or mass
    facultative.

• Independent

  • Adjective
    opt-in, option, non-compulsory, permissive, mandatory, optionally, voluntary, non-statutory, selective, compulsory, options.
  • Proper noun, singular
    Rights, Children, careers, option, Cas, optionally, voluntary, options.
  • Noun, plural
    electives, institutions, options.
  • Noun, singular or mass
    option.
  • Verb, past participle
    signed, used.

Antonyms for Optional:

• adj.

  • all
    obligatory.
  • possible; available as choice
    forced, required, compulsory.
  • Other antonyms:
    imposed, prerequisite, nonelective, necessary, nonvoluntary, indispensable, incumbent on, essential, requisite, de rigueur, bounden.

• Other antonyms:

  • n.
    appointed, appointive, coercive, obligate.