题目内容：

when while as 过去进行时的用法

优质解答

这三个词 据我所知没有时态用法的区别
1.when 是指某个时间所发生的事,用于在完成时态
while是指某个时间段所发生的事,用于进行时态
2.①when意为"在……时刻或时期",它可兼指"时间点"与"时间段",所引导的从句的动词既可以是终止性动词,也可是持续性动词.如：
When I got home,he was having supper.我到家时,他正在吃饭.
When I was young,I liked dancing.我年轻时喜欢跳舞.
②while只指"时间段",不指"时间点",从句的动词只限于持续性动词.如：
While I slept,a thief broke in.在我睡觉时,盗贼闯了进来.
③when从句动词为终止性动词时,不能由while替换.如：
When he came yesterday,we were playing basketball.昨天他来时,我们正在打篮球.
④当从句的谓语是表动作的延续性动词时,when,while才有可能互相替代.如：
While / When we were still laughing,the teacher came in.正当我们仍在大声嬉笑时,老师进来了.
⑤当从句的谓语动词是终止性动词,而且主句的谓语动词也是终止性动词时,when可和as通用,而且用as比用when在时间上更为紧凑,有"正当这时"的含义.如：
He came just as (or when) I reached the door.我刚到门那儿,他就来了.
⑥从句的谓语动词如表示状态时,通常用while.如：
We must strike while the iron is hot.我们应该趁热打铁.
⑦while和when都可以用作并列连词.
Mike is tall while his brother is short.迈克的个子很高,然而他弟弟很矮.
Mary was on her way home when two big boys stopped her.玛丽正走在回家的路上,这时两个大个子男孩拦住她.
while可以表示对比 如
i like coffee while Tom like milk.
as与when,while都是引导时间状语从句的从属连词,含义都是"当……的时候".但它们有区别：用when时,从句的动作可以与主句的动作同时发生,也可以先于主句的动作发生；用while时,从句的动作为一过程,主句动作与从句动作同时进行或在从句动作过程中发生；用as时,主句和从句的动作同时发生,具有延续的含义.例如：
(1)It was raining when he got to the airport.他到达工地时,天正在下雪.
(2)someone knocked at the door while paul‘s mother was cooking.有人敲门的时候保罗的母亲正在做饭.
(3) You will grow wiser as you grow older.你会随着年龄的增长而越来越聪明