while的用法

while是表示“当。。。。的时候”后面跟点动词，也就是终止性动词。可以和WHEN换。不过WHEN跟的是延续性动词，和过去式。

while 一段时间；当……时（和……同时）；却

（1）I”ll be back for a while

（2）He fell asleep while doing homework.

（3）John was dressed in brown while Mary was dressed in blue

连词while大致有以下四种用法:

1.引导时间状语从句,意为"当……的时候;和……同时",此时的主从句谓语动作同时发生,从句谓语通常是延续性动词。如:

Mary watched TV while she ate her supper.玛丽边吃饭边看电视。

While she was listening to the radio, she fell asleep.她听着收音机睡着了。

while引导从句时,如主从句的主语一致,且从句谓语又含有be,则从句主语和be可省略。while后可直接跟现在分词、名词、形容词或介词短语。如:

We are teachers while (we are) serving as students.我们边当老师边当学生。

While (he was) yet a youth, he gained many prizes.他年轻时就曾多次获奖。

He caught a cold while(he was) on vacation.他度假时患了感冒。

2.表示对比或转折,意为"而;然而"。此时,while一般位于句中。如:

Some people waste food while others haven't enough.有些人浪费粮食,然而有些人却吃不饱。

You like sports, while I pref