when的用法知多少

华冰

when是历年各地高考英语试卷考查得较为频繁的一个词，其用法是多种多样的，下面就对其用法作简单的小结，并辅之以例句。

1. 作疑问副词，引导特殊问句，意思是“什么时候，何时”。

When will he leave？

2. 作连接副词，引导名词性从句或不定式短语，意思是“什么时候”。如：

I remember when this used to be a quiet village.

Id like to know when they will come.

When we shall have our English evening party is still a question.

Have you decided when to go sightseeing？

3. 作疑问代词，常与介词since， till， up to等连用，意思是“……时候”。如：

Since when/what time have they had the house？

Till when is the library open？

They left on Monday， since when （=since Monday） we have heard nothing.

4. 作关系副词，引导限定性定语从句和非限定性定语从句。如：

The day when/on which they were to leave finally arrived.

At the time when I saw him， he was well.

上面两句中的when均可换用that。

The film brought the hours back to me when I was take good care of in that faraway village.

Sunday is a holiday， when people do not go to work.

I will see you in October， when I come back.

5. 在某些含有“时间”的名词词组后面，由于该名词不表示时间，或整个名词词组已用作连词，不宜用when來引导。如：

This is the first time （that） I have read an English novel in the original.

Each time he came， he would bring us some good news.

I called on him the day I returned home.

6. 作从属连词，引导状语从句，表示多种语法意义。

（1）表示时间，有“当……时，在……的时候”的含义，此时when后面的从句是用来说明前面主句动作发生的背景。如：

Dont be afraid of asking for help when it is needed.

James pretended to be deaf when I spoke to him.

（2）表示条件，意思上接近“在……的情况下”，相当于if，有“如果，要是”的含义。如：

Come when you are ready.

Please turn off the switch when anything goes wrong with the machine.

（3）表示对比，相当于whereas， while，有“虽然，可是，而”的意思。如：

He usually walks when he might ride.

Why are you here when you should be in school？

（4）表示时间，相当于as soon as，有“一……就”的意思。如：

We will start when the team leader comes.

（5）相当于considering that， although， as，有“既然，考虑到，虽然”的意思，从句说明主句的理由。如：

I cant tell you anything when you wont listen.

Why do you want a new job when youve got such a good one already？

（6）表示某事突然发生，相当于and just at that time， and then，有“正在这时，这时突然”的意思。如：

I was getting up when the doorbell rang.

She was about to leave the office when it began to rain.

（7）表示“刚刚……就，还没……就”的含义，表示主、从句的动作几乎同时发生。主句常为过去完成时，并与just， hardly等连用，从句为过去时。如：

I had hardly opened the door when he hit me.

I had hardly/barely/scarcely finished writing my letter when I heard a knock at the door.

（8）有“正……忽然……”的含义，表示突然发生某事。when之前的主句说明when之后的从句动作发生的背景。如：

I was about to leave my office when the telephone rang.

在这种句型中，一般不能将when放在句首。

（9）有“无论什么时候……”的含义，与whenever的意思差不多，但语气较轻。此时when后的从句说明主句动词动作发生的背景。如：

When the wind blows， all the doors rattle.

（10）有“本该（可）……而（却）……”的含义，此时when含有对比意义。如：

They have only three copies when we need five.

（11）有“那时”或“然后”的含义，此时when前往往有逗號。例如：

They arrive at 6， when we all have dinner.

（12）有“其实或虽然……但是……”的含义，此时when的意思接近although。如：

She stopped trying， when she might succeed next time.

（13）when引导状语从句时，在不影响文章意思情况下往往将从句的某些成分省去，因此常常会出现以下结构。

①when+现在分词。如：

when sleeping， I never hear a thing.

②when+过去分词。如：

This dictionary will look nice when printed.

③when+名词或形容词。如：

When a boy， he was sick all the time.

④when+介词短语。如：

When at Rome do as Romans do.

7. 由when等引导的状语从句，如果其主语与主句的主语一致或是it，谓语动词又含有be时，主语和be常常被省去，只保留连词、表语或分词（短语）。如：

When （I was） a boy， I went to swim in the lake every summer.

When （we are） young， we are full of hope and anxieties.

Metals expand when heated and contract when cooled.

8. 在表示同时，即“在……的时候”时，常可与while， as互换使用。如：

When/While/As I was taking a wilk in the park， I saw two men fighting.

9. 有时可以代替whenever，意思是“任何时候”。如：

Come when（ever） you please.

You may begin when（ever） you are ready.

10. when也可作名词，意思是“时间”。如：

Please tell me the when and（the） how of it.

He asked them the when and（the） where of the traffic accident.