A
By (+ a time) = no later than:
- I sent the letter to them today, so they should receive it by Monday.
(= on or before Monday, no later than Monday) - We’d better hurry. We have to be home by 5:00
(= at or before 5:00, no later than 5:00) - Where’s Sue? She should be here by now.
(= now or before now – so she should have arrived already)
B
We use until (or till) to say how long a situation continues:
– “Shall we go now?” “No, let’s wait until (or till) it stops raining.”
– I couldn’t get up this morning. { I stayed in bed until half past ten. / I didn’t get up until half past ten. }
Compare until and by:
-—————————–
Something continues until a time in the future:
– Fred will be away until Monday.
(so he’ll be back on Monday)
– I’ll be working until 11:30.
(so I’ll stop working at 11:30)
-—————————–
Something happen by a time in the future:
– Fred will be back by Monday.
(= he’ll be back no latter than Monday)
– I’ll have finished my work by 11:30.
(= I’ll finish my work no later than 11:30)
-—————————–
C
You can say “by the time something happens.” Study these examples:
– It’s too late to goto the bank now. By the time we get there, it will be closed.
(= the bank will close between now and the time we get there)
– (from a postcard) Our vacation ends tomorrow. So by the time you receive this postcard, I’ll be back home.
(= I will arrive home between tomorrow and the time you receive this postcard)
– Hurry up! By the time we get to the theater, the play will already have started.
You can say “by the time something happened” (for the past):
– Karen’s car broke down on the way to the party last night. By the time she arrived, most of the other guests had left.
(= It took her a long time to get to the party and most of the guests left during this time)
– I had a lot of work to do last night. I was very tired by the time I finished.
(= It took me a long time to do the work, and I became more and more tired during this time)
– We went to the theater last night. It took us a long time to find a place to park.
By the time we got to the theater, the play had already started.
Also by then or by that time:
– Karen finally arrived at the party at midnight, but by then (or by that time), most of the guests had left.
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