while\ as \when有何区别

while与when以及as之间的区别。1。当从句中的谓语动词是持续性的动作时,我们可以用while,when或as。While / When / As I was walking down the street,I noticed a police car in front of the bank。我顺着马路往前走时,发现银行门前停着一辆警车。2。当从句中的谓语动词表示瞬间动作时,不可用while。He was on the point of leaving when someone knocked at the door。他正要走,这时有人敲门。3。如果谈论两个长动作,最常用的是while。While John was sitting biting his nails,I was working out a plan to get us home。约翰坐在那里咬指甲时,我想出了一个回家的办法。不过,as是可以用来说明两种正在发展或变化的情况的,这时as引导一个持续性的动作,主句中的动作与之同时进行。As we talked on,he got more and more excited。我们继续往下谈的时候,他越来越兴奋。4。如果表示两个短动作或事件同时发生,最常用的是as或just as,也可用when。Just as he caught the ball,there was a tearing sound。当他抓住球的时候,有一种撕裂的声音。I thought of it just when you opened your mouth。就在你要说话的时候,我也想到了。