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它们的区别如下:
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。
如:
①Why do you want a new job when you've 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?
②Sorry,I was 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。
③Strike 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。
④The 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。
如:
①When he had finished his homework,he took a short rest.(finished先发生)
当他完成作业后,他休息了一会儿。
②When 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。
如:
①When /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。
②When /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,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)
随着时间的推移,天气变得更糟。
三、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:
① 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.
② They were singing while we were dancing.
四、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:
①The children were running to move the bag of rice when they heard the sound of a motor bike.
孩子们正要跑过去搬开那袋米,这时他们听到了摩托车的声音。
②He is strong while his brother is weak.
他长得很结实,而他弟弟却很瘦弱。
同学可以戳[url=http://www.hjenglish.com/yufadaquan/p961892/]【while,as,when的区别】[/url]学习更多相关知识哦~
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