一、由when引導(dǎo)的時間狀語從句，主句用過去進行時，從句應(yīng)用一般過去時；
When the teacher came in, we were talking.
老師進來時，我們正在談話。

二、when既可表示某一點時間，也可以表示某一段時間 。在when引導(dǎo)的時間狀語從句中，其謂語動詞可以是延續(xù)性的，也可以是非延續(xù)性的，可與主句中的謂語動詞同時發(fā)生，也可在其后發(fā)生。例如：
1. I was just reading a book when she came into my room.
她走進我房間時，我正在看書。
2. When he was a child he was always trying out new ideas.
他小時候就常常試驗一些新的設(shè)想。

三、下面的例子是一般過去時和過去進行時比較典型的搭配，表示一個動作在發(fā)生的過程中，又有另一個動作發(fā)生，when引導(dǎo)的是一個時間狀語從句。請看以下例句：
1. A woman saw it happen when she was walking past.
一位女子經(jīng)過正好看見這件事發(fā)生
2. Jane hurt her leg when she was swimming She didn’t notice the big rock in the river.
簡游泳時傷了腿，她沒有注意到河里的大石頭。
3. Tom dropped his camera when he was passing the bridge.
湯姆過橋時不慎將照相機掉了下去。

四、在將來時從句中，常用when，且從句須用一般時代替將來時。
1.You shall borrow the book when I have finished reading it．
在我讀完這本書后，你可以借閱。
2.When the manager comes here for a visit next week，Ill talk with him about this．
下周，經(jīng)理來這參觀時，我會和他談?wù)劥耸隆?/p>

五、when用于表示“一……就……”的句型中（指過去的事情）。
sb．had hardly（＝scarcely） done sth．when．．．＝Hardly ／ Scarcely had sb．done sth．when．．．
1.I had hardly ／scarcely closed my eyes when someone knocked at the door．＝Hardly ／ Scarcely had I closed my eyes when someone knocked at the door．
我剛一閉上眼，就有人在敲門了。
2.I had hardly ／scarcely entered my room when the telephone rang．＝Hardly ／Scarcely had I entered my room when the telephone rang．
我剛一走進房門，電話就響了。