用于肯定句中：
1) It may last until Friday.这可能要延续到星期五.
2) He will be working until 5 o'clock.他将一直工作到五点钟.
3) She was a bank clerk until the war,when she trained as a nurse.她战前是个银行职员,战时受训当了护士.
不难看出until 用于肯定句中,表示句子的动作一直持续到until短语所表示的时间为止,即表示动作的终点.一般可译为“直到……时(为止)”或“在……以前”.在这种用法中,句子的谓语动词必须是持续动词(非瞬间动词),如live,wait ,last,love,like,stay,work,continue 等.
用于否定句中：
1) The secret was never told until after the old man's death.这个秘密在老人去世后才说出来.
2) Don't open it until your birthday.等到你过生日那天再打开.
3) She didn't sleep until eight.她八点钟才睡觉.
不难看出until用于否定句中,表示句子的动作直到until短语所表示的时间才开始发生,即表示动作的起点.一般译为“直到……才”或“直到……之前(……还不)” .