when 的用法

when 的用法

一、when 用作副词。

1. 用作疑问副词，引导特殊疑问句。(什么时候，何时[at what time ])例如：

①When will you come to see me?

②When are they going to visit the Great Wall?

2. 用作连接副词，通常用来引导名词性从句[主语从句、表语从句、同位语从句、宾语从句]及起名词作用的“ when ＋动词不定式”结构。(什么时候，何时[at which; on which ])例如：

①When he comes is not known. [主语从句]

②The morning is when I am busiest. [表语从句]

④I don't know when the plane takes off. [宾语从句]

⑤I don't know when to leave for London. [宾语]

3. 用作关系副词，引导限定性定语从句和非限定性定语从句。(在…的时候[at/on/in/during which])例如：

①Do you still remember the days when we stayed in America?

②The day will come soon when the Chinese astronauts will go to the moon.

③It happened ten years ago, when I was a child.

④We will go to the countryside at the beginning of June, when the summer harvest will start.

二. when 用作连词。

1. 用作从属连词，意为“当……的时候[at the time when ]”，引导时间状语从句。例如：

①They learned a lot from the peasants when they stayed in the village.

②It was snowing when he arrived at the station.

【点津】如果when 引导的从句中的主语和主句中的主语一致，且从句中的谓语动词是“ be ＋分词”或从句主语是it ，则be 动词及其主语常可省略。例如：

③When（he was ）asked why he was late, he made no answer.

④I'll tell him about it when（it is ）possible.

2. 用作从属连词，意为“一……就……”，引导时间状语从句。[immediately after]例如：

①We will stand up when the teacher comes into the classroom. 老师一进

教室我们就起立。

②Fire the rockets when I give the signal.

3. 用作从属连词，意为“还没/ 刚刚/刚一……就”，引导时间状语从句。[immediately after]例如：

①I had hardly opened the door when he came in. 我刚一开门，他就进来了。

②I had not been reading for half an hour when I heard someone call my name.

【点津】hardly…when和no sooner…than的结构要注意三点：意思为“一A就B“；A句通常用完成时态；hardly 和no sooner 位于句首时要注意部分倒装。

4. 用作从属连词，意为“倘若，如果”，表示条件。例如：

①Turn off the switch when anything goes wrong with the machine. 如果机器发生故障，就把电源关上。

②He will be likely to recover when he is operated on.

5. 用作从属连词，意为“既然，尽管”，表示让步。例如：

①Why use metal when you can use plastic?既然能用塑料,为什么用金属?

②They kept trying when they knew it was hopeless. 尽管他们知道那件事没有希望，可是他们还在不断地努力。

6. 用作并列连词，意为“在那时，届时;就在这时”，表示时间。这时主句中可以用过去进行时，过去完成时或“ was/were about to do sth. ”结构。

①Last night I was about to go to bed when the phone rang.

②I was cooking in the kitchen when someone knocked at the door.

③He had just finished the book when supper was served.

7. 用作并列连词，意为“虽然、然而、可是”，表示转折。例如：①He usually walks to work when he might take a bus. 虽然他可以坐公共汽车上班，但他却常常步行上班。

②I had only twenty dollars when I needed thirty to buy the dictionary.我需要30 美元买那本字典，可是我只有20美元。

8. 用作并列连词，意为“而、却”，表示对比。例如：

How can he say that everything is fine when it's obvious that it is not? 他怎能说一切都好呢？情况显然不是那样。

三. when 用作代词[which time]。

when 作为代词常常位于介词之后，意为“那时，什么时候”。例如：

①Since when have you been studying Japanese?

【点津】since when 作引导词时是“介词（since）+关系代词（when）” 的结构，when意为which time。since when常引导非限制性定语从句，从句应用完成时态。

②I came here in 1949, since when I have been engaged in this work. 我1949年到这里，从那时起我就担任这项工作。

③We came back on Tuesday, since when we have been working in the repair shop.

④We came a week ago, since when the weather has been bad.

四、when 还可用作名词，前面常常用定冠词the。the when 表示事件发生的时间,常常与the where, the how 并列使用。

He told the police the when and the how of the accident. 他告诉警察事故发生的时间及发生的原委。

［巩固练习］

1. I remember ______ this used to be a quiet village.

A. when

B. how

C. where

D. what

2. Why do you want a new job _____ you've got such a good one already?

A. that

B. where

C. which

D. when

3. It was an exciting moment for these football fans this year, ______ for the first time in years their team won the World Cup.

A. that

B. while

C. which

D. when

4. We are living in an age _______ many things are done on computer.

A. which

B. that

C. where

D. when

5. The reporter said that the UFO ______ east to west when he saw it.

A. was travelling

B. travelled

C. had been travelling

D. was to travel

6. ______ got into the room _________ the telephone rang.

A. He hardly had; then

B. Hardly had he; when

C. He had not; than

D. Not had he; when

7. ---- Can I join your club, Dad?

---- You can when you _______ a bit older.

A. get

B. will got

C. are getting

D. will have got

8. I shall never forget those days ________ I lived in the countryside with the farmers, ________ had a great effect on my life.

A. that; which

B. when; which

C. which; that

D. when; who

9. The film brought the hours back to me ______ I was taken good care of in that faraway village.

A. until

B. that

C. when

D. where

10. He was about to tell me the secret ______ someone patted him on the shoulder.

A. as

B. until

C. while

D. when

11. My brother left school in 2005 ,and since then he ______in Beijing .

A. lives

B. lived

C. will live

D. has lived

12. Tom left Shanghai for London on May 5 , since___I have never called him up.

A when

B then C. while D. that

Key

1. ADDDA 6. BABCD 11. DA