8 比较while, when, as

1）as, when 引导短暂性动作的动词。例如：

　 Just as / Just when / When I stopped my car, a man came up to me. 我一刹车，有一个人向我走来。

2）当从句的动作发生于主句动作之前，只能用when 引导这个从句，不可用as 或 while。例如：

　 When you have finished your work, you may have a rest. 赶完活后，你可以休息一下。

3）从句表示"随时间推移"连词能用as，不用when 或while。例如：

　 As the day went on, the weather got worse.　日子一天天过去，天气越变越坏。

返回状语从句目录

9 比较until和till

此两个连词意义相同。肯定形式表示的意思是"做某事直至某时"，动词必须是延续性的。否定形式表达的意思是"直至某时才做某事"。动词为延续性或非延续性都可以。正确使用这两个连词的关键之一就在于判断句中的动词该用肯定式还是否定式。肯定句：I slept until midnight. 我一直睡到半夜时醒了。

Wait till I call you. 等着我叫你。（在肯定句中可用before代替。例如 Let’s get in the wheat before the sun sets.）

　 否定句：She didn’t arrive until 6 o’clock. 她直到6点才到。

　 Don’t get off the bus until it has stopped. 公共汽车停稳后再下车。

I didn’t manage to do it until you had explained how. 直到你教我后，我才会做。

区别：1）until可用于句首，而till通常不用于句首。例如：

Until you told me, I had heard nothing of what happened. 直到你告诉我以前，出了什么事我一点也不知道。

2）until when 疑问句中，until要放在句首。例如：

　 ---Until when are you staying?　你呆到什么时候？

--- Until next Monday.　呆到下周一。　

注意：否定句可用另外两种句式表示。

1）Not until…在句首，主句用倒装。例如：

Not until the early years of the 19th century did man know what heat is. 直到19 世纪初，人类才知道热为何物。

　Not until I began to work did I realize how much time I had wasted. 直到工作，才认识到我已蹉跎了几多月。

2）It is not until… that… 。例如：

It was not until I began to work that I realized how much time I had wasted.

10 表示"一…就…"的结构

　 hardly/scarcely…when/before, no sooner…than　和as soon as都可以表示"一…就…"的意思。例如：

　 I had hardly / scarcely got home when it began to rain. 刚回家，就下起雨来了。