WHEN与WHILE用法区别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。when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。while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when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
