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1、when while as since引导时间状语从句的区别一、when可以和延续性动词连用,也可以和短暂性动词连用;而while和as只能和延续性动词连用。Why do you want a new job when youve got such a good one already?(get为短暂性动词)你已经找到如此好的工作,为何还想再找新的?2从句动作和主句动作同时发生,且从句从句动作为延续性动词时,when,while,as都可使用。When While As we were dancing,a stranger came in(dance为延续性动词)当我们跳舞时,一位陌生人走了进
2、来。When While As she was making a phonecall,I was writing a letter(make为延续性动词)当她在打电话时,我正在写信。3当主句、从句动作同时进行,从句动作的时间概念淡化,而主要表示主句动作发生的背景或条件时,只能用 as。这时,asas常表示常表示“随着随着”;“一一边边,一,一边边”之意之意。As the time went on,the weather got worse(as表示“随着”之意)The atmosphere gets thinner and thinner as the height increases 随着高
3、度的增加,大气越来越稀薄。As years go by,China is getting stronger and richer 随着时间一年一年过去,中国变得越来越富强了。The little girls sang as they went 小姑娘们一边走,一边唱。4在将来时从句中,常用when,且从句必须用一般时代替将来时。When the manager comes here for a visit next week,Ill talk with him about this下周,经理来这参观时,我会和他谈谈此事。三、when用于表示“一就”的句型中(指过去的事情)。sbhad hard
4、ly/scarcely done sthwhenHardly Scarcely had sbdone sthwhen 我刚一闭上眼,就有人在敲门了。I had hardly scarcely closed my eyes when someone knocked at the doorHardly Scarcely had I closed my eyes when someone knocked at the door四、since引导的时间状语从句since引导的时间状语从句 动词可以是延续性动词,也可以是终止性动词,都表示动作或状态的结束,但汉语意思不同,这点在理解时要特别注意。1若si
5、nce引导的状语从句的谓语是终止性动词的过去时,则从句表示的时间是“从动作开始的那一时刻起”。例如:He has studied very hard since he came to our school.自从他来到我们学校,他学习就非常努力。We have been missing them since they left here自从他们离开这里,我们就一直很想念他们。2若since引导的状语从句的谓语动词是持续性动词或表示状态动词的过去时时,则从句表示的时间是“从动作或状态结束时算起”。例如:I havent heard any noise since I slept.Sleep 为持续
6、性动词,sleep的动作结束时,即“醒来”时,所以这句应译为“我醒后还未听到任何声音”。It is three years since he was a teacher.3若since引导的状语从句的谓语为持续性动词的现在完成时,则表示动作和状态延续到现在(说话时刻),其表示的时间的起点应从动作发生之时算起。例如:I havent heard from him since he has lived there。这里has lived表示动作的持续性,时间的起点应从:“开始居住”时算起。因此此句可理解为“自从他(开始)住在那儿起,我就一直没收到他的来信”。五、Since在特殊句型中的应用 句型句
7、型I:“It is(has been)+时间+since+持续性动词的过去时”,表示“自从以来到现在已有多久。”例如:It has been quite some time since I was last in London.我上次离开伦敦至今颇有一段时间了。句型句型II:“It was+时间+since+持续性动词的过去完成时”,表示“从到过去某时间点以来”。例如:It was three years since we had been here.那时我们在这已呆了三年。至于It is+一段时间+since的句型与It has been+一段时间+since意思相同。前者是规范说法,后者是
8、口语说法。应注意的是,在这种结构中,since引导的从句绝对不能用否定式的谓语动词来表示否定意义,下面两句都错了:It is a long time since he didnt study English.Its two months since you didnt come to see me.正确的说法为:Its a long time since he studied English 他好久没学英语了。You havent come to see me for two months.你有两个月没来看我了。延续性动词和短暂性动词延续性动词表示能够延续的动作,这种动作可以延续下去或产生持久
9、影响,又叫非点动词。常见的这类动词有:study,work,stand,lie,know,walk,keep,have,wait,watch,sing,read,sleep,live,stay,smoke等。延续性动词的用法很广,常见于现在完成时中的句子中,且常与for,how,long,since等引导的表示一段时间的状语或状语从句连用。终止性动词也称非延续性动词、瞬间动词或短暂性动词,表示不能延续的动作,这种动作发生后立即结束。如open,close,finish,begin,come,go,arrive,reach,get to,leave,move,borrow,buy,die等。终止性动词又叫点动词,可用于现在完成时态,但由于动作是瞬时间完成的所以不能与for或since引出的时间状语连用。英语中常见的非延续性动词在完成时态中可改为相应的表示延续性的动词或短语,这时可与表示一段时间的的状语连用。结束语结束语谢谢大家聆听!谢谢大家聆听!20