在复合句中 ， 修饰名词或代词的从句叫定语从句 ， 被修饰的名词或代词叫先行词 ， 引导定语从句的有关系代词 who, whom, whose, which, that等和关系副词where, when, why等 ， 关系代词和关系副词在定语从句中担任句子成份。

1.由who引导的定语从句中 ， who用作主语 ， 如 ： This is the boy who often helps me.

2.由whom引导的定语从句中，whom用作宾语，如：The man whom you are waiting for has gone home.

3.由whose引导的定语从句中 ， whose用作定语 ， 如 ： Do you know the girl whose skirt is white?

4.由which引导的定语从句中，which用作主语或谓语动词的宾语或介词的宾语，如：

The room in which there is a machine is a work shop.

The river which is in front of my house is very clean.

This is the pen which you want.

注意 ：

(1)whom, which用作介词宾语时 ， 介词可放在 whom、which之前 ， 也可放在从句原来的位置上；但在含有介词的动词固定词组中，介词只能放在原来的位置上。如： He is the very person whom we must take good care of.

(2)引导非限制性定语从句时，必须用关系代词which，不用that,如：I have lost

my bag, which I like very much.

(3)关系代词在句中作主语时，从句的谓语动词的人称和数必须和先行词保持一致。

5.由that引导的定语从句中，that可以指人或物，在从句中作主语或谓语动词的宾语，但不能放在介词后面作介词宾语，如：

The book that I bought yesterday was written by Lu Xun.

注意在下面几种情况下必须用 that引导定语从句。

(1)先行词是不定代词all, few, little, much, something, nothing, anything等 ， 如 ：

All that we have to do is to practise English.

(2)先行词被序数词或形容词最高级所修饰，如

The first letter that I got from him will be kept.

(3)先行词被all, any, every, each, few, little, no, some等修饰 ， 如

I've eaten up all the food that you gave me.

(4)先行词被the only, the very, the same, the last修饰时如

He is the only person that I want to talk with.

(5)先行词既有人又有物时，如:

They talked about persons and things that they met.

(6)当句中已有who时 ， 为避免重复 ， 如 ： Who is the man that is giving us the

class?

6.由when, where, why引导的定语从句，如:

I don't know the reason why he was late.

This is the place where we have lived for 5 years.

I'll never forget the day when I met Mr Li for the first time.

注意：先行词是表示地点时，如果从句的谓语动词是及物的，就用 that(which)，如果从句的谓语动词是不及物的，就用where引导。This is the house Which /that he has lived in for 15 years.(Where he has lived for 15 year.)

7. 限制性定语从句和非限制性定语从句

(1)限制性定语从句是句中不可缺少的组成部分，主句和从句之间不用逗号分开。引导非限制性定语从句的关系代词有who, whom, whose, which, of which等，这些关系代词都不能省略。

(2)非限制性定语从句是对主句先行词的补充说明 ， 没有这种从句 ， 不影响主句意思的完整 ， 一般用逗号把主句和从句分开 ， 关系代词用 which,不用that;指人时可用who,如 ： I have two brothers, who are both students.

8．如何简化定语从句

（1）.定语从句简化为形容词或形容词短语作后置定语。如:

My grandfather lives in a village that is far away from here.

→My grandfather lives in a village far away from here.我祖父住在离这儿很远的一个村子。

This is a book that is worth reading.

→This is a book worth reading. 这是一本值得看的书。

（2） 定语从句简化为现在分词或现在分词短语作前置或后置定语。

The man who is standing under the tree is our English teacher.

→The man standing under the tree is our English teacher.

站在树下面的那个人是我们的英语老师。

I saw the house that was burning at that time.→I saw the burning house at that time.

当时我看到那房子在燃烧。

（3）定语从句简化为过去分词短语作后置定语。

I like to see the films which are directed by Zhang Yimou.→I like to see the films directed by Zhang Yimou. 我喜欢看张艺谋导演的电影。

She is the girl who was praised at the school meeting.→She is the girl praised at the school meeting. 她就是在校会上受表彰的那个女孩。

（4）定语从句简化为不定式作后置定语。

He is always the first person that comes to school.→He is always the first person to come to school.他总是第一个到校。

The report which will be given tomorrow is important to us.→The report to be given tomorrow is important to us. 明天要作的报告对我们很重要。

（5）定语从句简化为what 从句。

I couldn't remember the words that he said.→I couldn't remember what he said.

我记不得他说的话。

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