Synonyms of once in English:

once


See definition of once

adverb

1‘I saw him only once’

SYNONYMS
on one occasion, one time, one single time
ANTONYMS

twice, many times

2‘he did not once help’

SYNONYMS
ever, at any time, on any occasion, at all, under any circumstances, on any account, in a million years

3‘they were friends once’

SYNONYMS
formerly, previously, in the past, at one time, at one point, once upon a time, on a former occasion, on one occasion, one time, in one case, time was when, in days gone by, in times gone by, back in the day, in times past, in the old days, in the good old days, long ago
archaic sometime, erst, erstwhile, whilom
literary in days of yore, in times of yore, of yore
ANTONYMS

now


conjunction

1‘he'll be all right once she's gone’

SYNONYMS
as soon as, when, after, immediately after, the instant, the minute, the moment, the second
British informal immediately

Phrases

    at once

    1‘you must leave at once’


    SYNONYMS

    immediately, right away, right now, this instant, this minute, this moment, this second, now, straight away, instantly, instantaneously, directly, suddenly, abruptly, summarily, forthwith, promptly, without delay, without hesitation, without further ado

    quickly, as fast as possible, as soon as possible, fast, speedily, with all speed

    informal

    like a shot, in a flash, like a flash, before you can say Jack Robinson, in two shakes, in two shakes of a lamb's tail

    ANTONYMS

    later, in due course

    2‘all the guests arrived at once’


    SYNONYMS

    at the same time, at one and the same time, at the same instant, at the same moment, together, all together, simultaneously

    as a group, in unison, in concert, in chorus

    ANTONYMS

    singly, in dribs and drabs

    once and for all

    1‘you must decide once and for all’


    SYNONYMS

    conclusively, decisively, finally, positively, absolutely, determinedly, definitely, definitively, irrevocably

    2‘he has gone once and for all’


    SYNONYMS

    for good, for always, forever, permanently, finally, in perpetuity

    informal

    for keeps

    once in a while

    ‘once in a while a car went past’


    SYNONYMS

    occasionally, from time to time, now and again, now and then, every now and again, every now and then, every so often, every once in a while, on occasion, on occasions, on the odd occasion, at times, sometimes, off and on, at intervals, periodically, sporadically, spasmodically, erratically, irregularly, intermittently, by fits and starts, in fits and starts, fitfully, discontinuously, piecemeal

    rare

    interruptedly