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Common Mistakes and Confusing Words in English
|by vs until||
Both until and by indicate any time before, but not later than.
Until tells us how long a situation continues. If something happens until a particular time, you stop doing it at that time.
They lived in a small house until September 2003.
I will be away until Wednesday.
We also use until in negative sentences.
Details will not be available until January.
If something happens by a particular time, it happens at or before that time. It is often used to indicate a deadline.
You have to finish by August 31.
We also use by when asking questions.
Will the details be available by December?