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1、 when和while的区别when是at or during the time that, 既指时间点，也可指一段时间；while是during the time that，只指一段时间，因此when引导的时间状语从句中的动词可以是终止性动词，也可以是延续性动词，而while从句中的动词必须是延续性动词。when 说明从句的动作和主句的动作可以是同时，也可以是先后发生；while 则强调主句的动作在从句动作的发生的过程中或主从句两个动作同时发生。由when引导的时间状语从句，主句用过去进行时，从句应用一般过去时；如果从句和主句的动作同时发生，两句都用过去进行时的时候，多用while引导，如：

2、a. When the teacher came in, we were talking.当此句改变主从句的位置时，则为：While we were talking, the teacher came in.b. They were singing while we were dancing.when和while 还可作并列连词。when表示“在那时”；while表示“而，却”，表对照关系。如：a. The children were running to move the bag of rice when they heard the sound of a motor bike.孩子们正要跑

3、过去搬开那袋米，这时他们听到了摩托车的声音。b. He is strong while his brother is weak.他长得很结实，而他弟弟却很瘦弱。拓展：when，while，as引导时间状语从句的区别when，while，as显然都可以引导时间状语从句，但用法区别非常大。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？Sorry，I wa

4、s out when you called me（call为短暂性动词）对不起，你打电话时我刚好外出了。Strike while the iron is hot（is为延续性动词，表示一种持续的状态）趁热打铁。 The students took notes as they listened（listen为延续性动词）学生们边听课边做笔记。二、when从句的谓语动词可以在主句谓语动作之前、之后或同时发生；while和as从句的谓语动作必须是和主句谓语动作同时发生。1从句动作在主句动作前发生，只用 when。When he had finished his homework，he took a

5、short rest（finished先发生）当他完成作业后，他休息了一会儿。When I got to the airport，the guests had left（got to后发生）当我赶到飞机场时，客人们已经离开了。2从句动作和主句动作同时发生，且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，一位陌生人走了进来。When While As she was making a phone call，I was writing a lette

6、r（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，as常表示“随着”；“一边，一边”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

7、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。The sad mother sat on the roadside，shouting as she was crying伤心的妈妈坐在路边，边哭边叫。4在将来时从句中，常用when，且从句须用一般时代替将来时。You shall borrow the book when I have finished reading it在我读完这本书后，你可以借阅。When the manager comes here for a visit next week，Ill talk with him

8、 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 hardly（scarcely） done sthwhenHardly Scarcely had sbdone sthwhenI had hardly scarcely closed my eyes when someone knocked at the doorHardly Scarcely had I closed my eyes when someone knocked at the door我刚一闭上眼，就有人在敲门了。I had hardly scarcel

9、y entered my room when the telephone rangHardly Scarcely had I entered my room when the telephone rang我刚一走进房门，电话就响了。 终止性动词英语中，动词按其动作发生的方式、动作发生过程的长短，可分为延续性动词和终止性动词。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等 延续性

10、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影响。如：learn, work, stand, lie, know, walk, keep, have, wait, watch, sing, read, sleep, live, stay等。延续性动词表示的动作不但可以延续，而且可以产生持久的影响。常见的这类动词有：be，have，keep，know，learn，lie，live，read，sing，sleep，stand，stay，wait，walk，watch等。延续性动词的用法很广，但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。