at one time in the past; formerly:I was a farmer once; a once powerful nation.
a single time:We ate there just once. We go to a movie once a week.
even a single time; at any time; ever:If the facts once become known, it will be just too bad.
by a single step, degree, or grade:a cousin once removed.
Idiomsonce and again, repeatedly:He has been told once and again not to slam the door.
Idiomsonce and for all, decisively; finally:Let's settle this problem once and for all.Also, once for all.
Idiomsonce in a while, at intervals; occasionally:She stops in to see us once in a while.
Idiomsonce or twice, a very few times; infrequently:I've seen her in the elevator once or twice.
Idiomsonce upon a time, at some unspecified past time, esp. a long time ago:Once upon a time, in a faraway land, there lived a prince and princess.
former; having at one time been:the once and future king.
if or when at any time; if ever.
whenever; as soon as:Once you're finished, you can leave.
a single occasion; one time only:Once is enough.
Idiomsall at once:
simultaneously:The children were running, screaming, and throwing things all at once.
suddenly:All at once the rain came down.
at the same time; simultaneously:Don't all speak at once.
immediately; promptly:Tell him to come at once!
bef. 1150; Middle English ones, Old English ānes, origin, originally genitive of ānone; replacing Middle English enes, Old English ǣnes once, equivalent. to ǣne once (origin, originally instrumental of ān) + -es adverb, adverbial suffix; see -s1