once

American  

[wuhns] / wʌns /

adverb

1. at one time in the past; formerly.

   I was a farmer once;

   a once powerful nation.

2. a single time: We go to a movie once a week.

   We ate there just once.

   We go to a movie once a week.

3. even a single time; at any time; ever.

   If the facts once become known, it will be just too bad.

4. by a single step, degree, or grade.

   a cousin once removed.

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adjective

1. former; having at one time been.

   the once and future king.

conjunction

1. if or when at any time; if ever.

2. whenever; as soon as.

   Once you're finished, you can leave.

noun

1. a single occasion; one time only.

   Once is enough.

idioms

1. once and again, repeatedly.

   He has been told once and again not to slam the door.

2. all at once,

   1. simultaneously.

      The children were running, screaming, and throwing things all at once.

   2. suddenly.

      All at once the rain came down.

3. at once,

   1. at the same time; simultaneously.

      Don't all speak at once.

   2. immediately; promptly.

      Tell him to come at once!

4. once upon a time, at some unspecified past time, especially a long time ago.

   Once upon a time, in a faraway land, there lived a prince and princess.

5. once or twice, a very few times; infrequently.

   I've seen her in the elevator once or twice.

6. once and for all, decisively; finally: Also once for all.

   Let's settle this problem once and for all.

7. once in a while, at intervals; occasionally.

   She stops in to see us once in a while.

once British  

/ wʌns /

adverb

1. one time; on one occasion or in one case

2. at some past time; formerly

   I could speak French once

3. by one step or degree (of relationship)

   a cousin once removed

4. (in conditional clauses, negatives, etc) ever; at all

   if you once forget it

5. multiplied by one

6. 1. conclusively

   2. occasionally

7. conclusively; for the last time

8. occasionally; now and then

9. a few times

10. used to begin fairy tales and children's stories

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conjunction

1. (subordinating) as soon as; if ever or whenever

   once you begin, you'll enjoy it

noun

1. one occasion or case

   you may do it, this once

2. 1. suddenly or without warning

   2. simultaneously

3. 1. immediately

   2. simultaneously

4. this time, if (or but) at no other time

once More Idioms  

More idioms and phrases containing once

• all at once
• at once
• every now and then (once in a while)
• give someone the once-over

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Etymology

Origin of once

First recorded before 1150; Middle English ones, Old English ānes, originally genitive of ān “one” replacing Middle English enes, Old English ǣnes “once,” equivalent to ǣne “once” (originally instrumental of ān ) + -es adverb suffix; see one, -s ¹

Explanation

If you try a new food one time and decide to never have it again, then you've only had it once, or one time. The word once has several meanings, each conveying the idea of something happening just one time. It can mean "on one occasion," like trying something only once to see if you like it. Once can also refer to something in the past that’s no longer true, as in, "I once lived there." Additionally, it can mean "as soon as," like "once you finish, we’ll leave." Each use of once describes a unique moment — whether one-time, past, or immediate.

Example Sentences

The most important thing is to ensure that once the mining has been conducted, the habitat can be returned to a state where the desert rain frog can inhabit it, he said.

From BBC • Jul. 9, 2026

Washington notes that late adopters who once resisted online banking and mobile apps are finally getting comfortable with digital payments.

From MarketWatch • Jul. 9, 2026

For the first time, players with a few years in the league could negotiate freely with any team once their contracts expired.

From The Wall Street Journal • Jul. 9, 2026

Each new shipment of sod that arrived in refrigerated trucks costs about $250,000 — and teams likely would have to replace that sod at least once during an NFL season.

From Los Angeles Times • Jul. 9, 2026

It’s as if they all agreed years before to meet here on this day, at this time, and fix what was once thought of as unfixable.

From "Split the Sky" by Marie Arnold

Related Words

• already
• before
• earlier
• formerly
• late
• previously