Synonyms for Once:

• adj.

  •dead (adjective)
  • late.
  •old (adjective)
  • primeval,
  • olden.
  •past (adjective)
  • ages ago.

• adv.

  •anyway (adverb)
  • ever.
  •in the past; occurred one time only (adverb)
  • already,
  • at one time,
  • back,
  • before,
  • bygone,
  • earlier,
  • erstwhile,
  • formerly,
  • heretofore,
  • late,
  • old,
  • one,
  • previously,
  • quondam,
  • sometime,
  • Whilom,
  • once upon a time,
  • in the olden days,
  • in the old days,
  • once only,
  • time was,
  • a single time,
  • back when,
  • but once,
  • in times gone by,
  • in times past,
  • on one occasion,
  • one time before,
  • one time previously,
  • only one time,
  • this time,
  • away back.

• adv

  •anyway (adverb)
  • at all.

• n.

  •
  • after,
  • beyond,
  • ensuing,
  • following,
  • subsequent,
  • subsequently,
  • succeeding,
  • Since.
  •
  • ago,
  • uniquely,
  • one day,
  • once only.
  •
  • already,
  • before,
  • earlier,
  • isolated,
  • one shot,
  • precede,
  • previously,
  • unrepeatable,
  • Aforetime,
  • Beforetime,
  • one-off.
  •formerly (noun)
  • earlier,
  • previously.
  •one time (noun)
  • one,
  • twice.

• Other synonyms:

  •
  • ago,
  • bygone,
  • hitherto,
  • immemorial,
  • Aforetime,
  • Beforetime,
  • Whilom.
  •
  • already,
  • backward,
  • earlier,
  • previously,
  • unrepeatable,
  • one-off.
  •
  • before,
  • isolated.
  •
  • past.
  •
  • late,
  • old,
  • previous.
  •
  • back.
  •alone
  • singly.
  •singular
  • one shot.
  •Other relevant words:
  • after,
  • ago,
  • ahead,
  • all at once,
  • alone,
  • already,
  • an,
  • ancient,
  • anciently,
  • antecedently,
  • antiquated,
  • antique,
  • anyway,
  • apart,
  • approach,
  • at a time,
  • at all,
  • at once,
  • at one time,
  • at times,
  • attack,
  • avenue,
  • back,
  • backward,
  • before,
  • beforehand,
  • behindhand,
  • beyond,
  • bout,
  • bygone,
  • channel,
  • close,
  • competition,
  • conclusively,
  • course,
  • dead,
  • deceased,
  • decidedly,
  • definitely,
  • dilatory,
  • direct,
  • directly,
  • earlier,
  • early,
  • elderly,
  • ensuing,
  • erst,
  • erstwhile,
  • ever,
  • eversion,
  • ex post facto,
  • finally,
  • following,
  • for good,
  • fore,
  • former,
  • formerly,
  • forward,
  • fresh,
  • heretofore,
  • hereupon,
  • history,
  • hitherto,
  • hornpipe,
  • identity,
  • immediate,
  • immediately,
  • immemorial,
  • in case,
  • in no time,
  • in one case,
  • individuality,
  • individually,
  • instant,
  • instantly,
  • isolated,
  • itinerary,
  • late,
  • lately,
  • latterly,
  • minute,
  • moment,
  • never,
  • no longer,
  • now and again,
  • now and then,
  • obsolete,
  • occasionally,
  • of late,
  • old,
  • olden,
  • older,
  • once and for all,
  • one,
  • one by one,
  • one shot,
  • one time,
  • oneness,
  • onetime,
  • originally,
  • other,
  • outdated,
  • particularly,
  • passage,
  • past,
  • path,
  • per se,
  • periodically,
  • positively,
  • post-haste,
  • precede,
  • prehistoric,
  • present,
  • previous,
  • previously,
  • primeval,
  • primitive,
  • prior,
  • prompt,
  • promptly,
  • quondam,
  • recent,
  • recently,
  • retrospectively,
  • right away,
  • road,
  • route,
  • sameness,
  • separately,
  • severally,
  • simultaneously,
  • single-handedly,
  • singly,
  • singularly,
  • sometime,
  • sometimes,
  • sort,
  • spell,
  • sporadically,
  • subsequent,
  • subsequently,
  • succeeding,
  • sudden,
  • suddenly,
  • then,
  • theretofore,
  • thereupon,
  • time,
  • together,
  • track,
  • twice,
  • uniquely,
  • unity,
  • unrepeatable,
  • used to,
  • way,
  • when,
  • whereupon,
  • while,
  • without delay,
  • yesterday,
  • yesteryear,
  • yet,
  • yore,
  • Aforetime,
  • Anywise,
  • Beforetime,
  • Erewhile,
  • If,
  • Since,
  • Thitherto,
  • Whenever,
  • Whensoever,
  • Whilom,
  • one-off,
  • pro hac vice,
  • straight away,
  • anytime,
  • once upon a time,
  • as soon as,
  • ere now,
  • till now,
  • in the past,
  • at any time,
  • in a jiffy,
  • in a trice,
  • at intervals,
  • by itself,
  • one day,
  • one fine day,
  • in the olden days,
  • in former times,
  • in olden times,
  • in the old days,
  • in time past,
  • some time ago,
  • for the nonce,
  • once only,
  • years ago,
  • no matter when,
  • time was,
  • at a stroke,
  • a single time,
  • ages ago,
  • back when,
  • before now,
  • but once,
  • in olden days,
  • in times gone by,
  • in times past,
  • on one occasion,
  • once for all,
  • one time before,
  • one time previously,
  • only one time,
  • this time,
  • per,
  • away back,
  • aeons ago,
  • in a wink.

Antonyms for Once:

• adj.

  • Other antonyms:
    coming, contemporary, current, extant, future, ongoing, present, present-day, prospective, unborn.

• adv.

  • in the past; occurred one time only
    currently, future, later, presently.

• Other antonyms:

  • n. t.
    in due course, later, now, singly, twice, many times, in dribs and drabs.