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when 和while的用法区别
两者的区别如下：

①when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。

②when 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。

③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：

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.

④when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。

先看两个词的所有用法,可以知道容易混淆的是1.和c.用法(如下)

while指
1.在做某事的期间,例:
He fell asleep while doing his homework.
2.与...同时
While Mary was writing a letter, the children were playing outside.
3.表示对比或相反的情况
I drink black coffee while he prefers it with cream.
4.虽然
While I admit that there are problems, I don't agree that they cannot be solved.

when指
a.在那时,其时
Sunday is the day when very few people go to work.
b.在那时,当时,当场
The Queen's last visit was in May, when she opened the new hospital.
c.当...时
It was raining when we arrived.
d.既然,考虑到
How can they learn anything when they spend all day watching TV?

从上面的例子也可以看出,while和when在表示"在...的时候"时有相近之处,但while一般后面跟持续性的动作,比如做作业,听歌之类,而when用在短暂性的动作,比如例子c.中的"到达"或者"进入房间".
现在你明白了吗?