英语：易错词汇短语辨析：when，while，as辨析

　　when，while，as考点辨析

　　when,while,as都能引导多种状语从句：

　　一、when常见考点

　　1、“当……时候”,引导时间状语从句。

　　When he was a young man，he was fond of hunting. It was already 10：00PM，when I finished the work.

　　2、“正在那时，这时”等于and at that time，引导时间状语从句。

　　We were having a meeting when someone broke in. We were about to leave when it began to rain.

　　3、“既然”等于since 或considering that， 引导原因状语从句。

　　It was foolish of you to take a taxi，when you should easily walk there in five minutes. How can they learn anything when they spend all their spare time watching TV?

　　4、“虽然，然而，可是”引导让步状语从句。

　　He usually walks when he might ride. They had only three chairs when they need five.

　　二、while常见考点

　　1、“当……时候”， 引导时间状语从句(从句动作必须是延续性的)。

　　Please don't talk so loud while others are working. While I was cleaning the window，my finger was seriously cut.

　　2、“虽然，尽管”相当于although，引导让步状语从句(常把while放在句首)。

　　While she is a top student， she has some shortcomings. While the Internet is bridging the distance between people， it may also be breaking some home or will cause other family problems.

　　3、“只要，如果”等于as long as，引导条件状语从句。

　　There is hope while there is life. While you study hard， your effort will pay off.

　　4、“而，然而”，表对比或相反的情况。

　　He likes pop music，while I am fond of folk music. Kids talk frequently about what they can do，while many adults do the opposite， tending to talk about what they can't .

　　三、as常见考点

　　1、“一边……一边”或“随着……”，引导时间状语从句(as引导的从句内部的动作与主句内动作同步)。

　　John sings as he works. (一边……一边)

　　Jame‘s blindness was getting worse as he was getting older.(随着……)

　　2、“因为”， 引导原因状语从句。

　　As you weren‘t there， I left a message. Perhapshe will need some help as he was ill.

　　3、“尽管，即使，虽然” 引导让步状语从句(用于形容词，副词或名词后构成部分倒装)。

　　Young as I am， I already know what career I want to follow. Much as I like you， I couldn't live with you. Child as Tom is ， he has been a success.