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

See Examples For:

once

Such systems can evaluate multiple inputs at once while making decisions informed by previous experiences and future priorities.

From Science Daily ● Aug. 17, 2026

Japanese macaques like this one - also known as snow monkeys - are about the size of a medium-sized dog once they reach adulthood.

From BBC ● Aug. 17, 2026

And once it’s all done, finance teams take a breath and gear up to do it again.

From The Wall Street Journal ● Aug. 17, 2026

Despite a solid start from Tarik Skubal, lackluster hitting once again proves costly for the Dodgers in a 6-2 loss to the first-place Milwaukee Brewers.

From Los Angeles Times ● Aug. 17, 2026

For once I’m glad that Nate isn’t here.

From "Red Flags and Butterflies" by Sheryl Azzam

Related Words

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