第 1 页精品文档---下载后可任意编辑新初三必看英语语法之 as、when 和 while 的区分Ⅰ. as "当(在)时候'往往可与 when 或 while 通用,但它着重指主句和从句的动作或事情相并发生。如: ① I saw him as he was getting off the bus. 当下公共汽车的时候,我观看了他。 ② As he walked on, he felt himself getting more and more tired.他连续往前走的时候,感到越来越疲乏。 Ⅱ. when "当(在)的时候'主句和从句的动作或事情可以同时发生,也可以先后发生。 ① It was raining when we arrived. 当我们到达的时候,正下着雨。 ② When we were at school, we went to the library every day. 我们在求学的时候,每天都到图书馆去。 Ⅲ. while "当(在)的时候'表主句的动作或事情发生在从句中的动作或事情的进展过程之中。从句通常为进展时态。它有时可与 when 通用,但它只能指一段时间(a period of time),而不能指一点时间(a point of time)如上面的第一个例子。又如: ① Please dont talk so loud while others are working. 别人在工作的时候,请勿大声讲话。 ② While I am washing the floor, you can be cleaning the windows.我洗地板时,你可以擦窗户。