while与when的区别

when, while这三个词都有"当……时候"之意,但用法有所不同,使用时要特别注意。 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。 辨析 ①when从句与主句动作先后发生时,不能与while互换。如： When he has finished his work, he takes a short rest。每当他做完工作后,总要稍稍休息一下。(when = after) When I got to the cinema, the film had already begun。当我到电影院时,电影已经开始了。(when=before) ②when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。 ③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。 ④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。 ⑤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。 ⑥while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。