After school, I was about to enter my apartment while I saw a little dirty dog lying beside a dustbin.这道改错题应该把while改成when，但是很多学生都改不出来，这就是不明白when和while的区别，那么它们到底该怎么用呢？
工具/原料
纸和笔
While用法
1
while表示当……时候，相当于when 英语解释为during the time that sth is happeningeg.Her parents died while she was still at school.她还在读书时，父母就去世了
2
while放在句中表示转折，对比，相当于buteg.He likes swimming while I like reading他喜欢游泳而我喜欢阅读
3
while放在句首翻译成虽然，尽管，相当于althougheg.While I am willing to help, I do not have much time available.尽管我愿意帮忙，但我没多少时间。
when的用法
at or during the time that 在……的时候，当……时eg.I loved history when I was at school.我上学时喜欢历史
区别
1
while引导的从句只能用延续性动词，而when引导的从句可以用延续性动词也可以用非延续性动词。
2
when引导的从句动作和主句动作可以同时发生或在之后发生，while只能同时发生或存在
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