文档介绍：状语从句
状语从句按其意义和作用可分为:
1、时间状语从句
引导时间状语从句的从属连词有:when, while, as, whenever, before, after, since, till, until, as soon as, once, hardly…when, no sooner…than等引导。如:
When he was still a young man, he was forced to leave his homeland for political reasons.
It has been 15 years since he left.
I’ll tell him the news as soon as I see him.
Once you have got used to it, you will like it.
I waited till he had finished his work.
注意:
(1)when, as, while
when即可引导持续性动作,又可引导短暂性动作。它可以表示主句的动作和从句的动作同时发生,或从句的动作发生在主句动作之前。如:
When I was a boy, I used to go to the seashore on Sundays.(同时)
When the lesson was over, we began our writing.
(从句动作在前)
as引导持续性动作,侧重主句和从句的动作同时发生。
He hurried home, looking behind as he went.
I saw your sister as she was getting on the bus yesterday.
He sang as he walked.
as也可表示“随着”,但要注意与with的区别:
As the day went on, the weather got even cold.(从句,故用谓语动词)
With the day going on, the weather got even cold.(介词,故用非谓语)
While:指的是“在某一时间里”, “在……期间”,从句里的动作必须是持续性的,它也强调主句和从句动作的同时发生,往往侧重主句和从句动作的对比。
如:
While he was in London, he studied music.
While we were watching TV, he was writing position.