By vs. Until

11.01.19 English Tips

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.
For example: They lived in a small house until September 2003. (They stopped living there in September.)

We also use until in negative sentences.
For example: Details will not be available until January. (January is the earliest you can expect to receive the details.)

If something happens by a particular time, it happens at or before that time.
It is often used to indicate a deadline.
For example: You have to finish by August 31. (August 31 is the last day you can finish; you may finish before this date.)

We also use by when asking questions.
For example: Will the details be available by December? (This asks if they will be ready no later than December.)

Until by も、共に「それよりも前で、それ以降ではない」ということを示します。

Until は、どのくらいその状況が続くということを表現します。
ある時までに何かが起こっている場合、その時を境にその状態ではなくなる時にuntil を使います。

また、否定文で until を使うこともあります。

ある時までに何かが起こり、それはその時かそれよりも前に終わる時、by を用います。
By は、よく締め切りを示す際に使われます。

また、質問をする時に by をよく使うこともあります。