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English definition of “once”

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once

adverb [not gradable]  /wʌns/ us  

once adverb [not gradable] (AT ONE TIME)

on or at a single time: I went to Disney World once. The book club meets once a month. Going to the Olympics is a once-in-a-lifetime opportunity (= a rare and valuable one).

once adverb [not gradable] (IN THE PAST)

in the past, but not now: I lived in Milwaukee once. Computers are much cheaper now than they once were.

once

conjunction  /wʌns/ us  

once conjunction (AS SOON AS)

as soon as, or when: Once you’ve tried their ice cream, you’ll be back for more.
(Definition of once from the Cambridge Academic Content Dictionary © Cambridge University Press)
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