用作状语的从句叫做状语从句,引导状语从句的关联词是某些从属连词,其在句子的位置可以置于句首、句末或句中,其中时间状语从句是它的一种。时间状语从句表时间,其关联词有as,after,before,once,since,till,until等。
As the twilight was beginning to fade,we heard the sound of a carriage.
当曙光开始消退时,我们听到了一架马车的声响
Once you’ve finished,go to bed.
你干完了再去睡觉
as,when,while虽都表时间,但是有区别的,as多用于口语,强调“同一时间”或“一先一后”,有时还有“随着”的含义,如
As I was going out,it began to rain.
当我出门时,开始下雨了(as强调两个动作紧接着发生,不强调开始下雨的特定时间,故须用as而不用when)
As spring warms the good earth,all flowers begin to bloom.
随着春回大地,百花开始绽放(句中的as也不可代之以when)
when则强调“特定时间”,如
When he was eating his breakfast,he heard the door bell ring.
当他正在用早餐时,听到门铃响了
while也表同一时间,其所表的时间不是一点,而是一段,如将上句的when改为while,while从句即强调“他吃早餐”的过程。
I didn’t wait a moment,but came immediately you called.
我一刻也没等待,你的电话一到我就来了(副词immediately引导时间状语从句,immediately=as soon as)
Next time you come,please bring your composition.
你下次来,请把你的作文带来(短语next time引导时间状语从句)
时间状语从句中有些成分有时可省略,如
Complete your work as soon as possible.
要把你的工作尽快完成(as soon as 后省去it is)
在时间状语从句中,通常不用将来时,而用现在时来代替,如
Be a pupil before you become a teacher.
先做学生,再做老师
I’ll tell her about that when I see her.
我见到她时会把这件事告诉她的
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