when可指時(shí)間點(diǎn)，可指時(shí)間段，從句中用延續(xù)性動(dòng)詞，也用非延續(xù)性動(dòng)詞；表示主句動(dòng)作發(fā)生在從句較長(zhǎng)動(dòng)作過(guò)程中，when, as均可使用。從句中為be動(dòng)詞，用when；when說(shuō)明從句的動(dòng)作和主句的動(dòng)作可以是同時(shí)發(fā)生，也可以是先后發(fā)生。由when引導(dǎo)的時(shí)間狀語(yǔ)從句，主句用過(guò)去進(jìn)行時(shí)，從句應(yīng)用一般過(guò)去時(shí)。

when的用法句型

1.be doing sth…when…

例：He was still smiling when the door opened and his wife came in.

他正笑著的時(shí)候門(mén)突然開(kāi)了，他妻子走了進(jìn)來(lái)。

2.be about to do sth…when…

例：We were about to start when it began to rain.

我們剛要出發(fā)，天就開(kāi)始下雨了。

3.had not done sth…when…/hardly…when…

例：He had not fallen asleep when the telephone rang.

他剛要入睡電話就響了。

4.had just done…when…

例：I had just gone to bed after a very hard day when the phone rang. 在勞累了一天之后我剛剛就寢，電話鈴就響了。