By (+ a time) = "no later than":
I mailed the letter today, so they should receive it by Monday. (= on or before Monday, no later than Monday)
We'd better hurry. We have to be hom 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)
Until은 이와 같은 의미로 사용할 수 없습니다:
Tell me by Friday whether or not you can come to the party. (not Tell me until Friday)
상황이 얼마나 오랫동안 지속되었는지를 이야기할 때 until(또는 till)을 사용합니다:
"Should 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.
until과 by의 비교:
until
어떤 일이 미래의 어느 때까지 지속됨:
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)
by
어떤 일이 미래의 어느 시점에 발생함:
Fred will be back by Monday. (= he'll be back no later than Monday)
I'll have finished my work by 11:30.
(I'll finish my work no later than 11:30)
by the time something happened:
(편지에서) I'm flying to Mexico this evening. So by the time you receive this letter, I'll be in Mexico City. (= I will arrive in Mexico City between now and the time you receive this letter.)
Hurry up! By the time we get to the theater, the play will already have started.
by the time something happened (과거에 대해):
Jane's car broke down on the way to the party last night. By the time she arrived, most of the guests had left. (= It took her a long time to get to the party, and most of guests went home during this time.)
I had a lot of work to do yesterday evening. 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 somewhere to part the car. By the time we got to the theater, the play had already started.
by then 또는 by that time:
Jane finally arrived at the party at midnight, but by then (or by that time), most of the guests had left.