twice

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If something happens twice, it happens two times, or there are two actions or events of the same kind.
You use twice in expressions such as twice a day and twice a week to indicate that something happens two times in each day or week.
If one thing is, for example, twice as big or old as another, the first thing is double the size or age of the second. People sometimes say that one thing is twice as good or hard as another when they want to emphasize that the first thing is much better or harder than the second.
Twice is also a predeterminer.
If you think twice about doing something, you consider it again and decide not to do it, or decide to do it differently.
once or twice&rarrsee once
twice over&rarrsee over