在复合句中，修饰某个名词或代词的句子（做这个名词或代词的定语）叫定语从句，定语从句一般放在被修饰的名词或代词后面，被修饰的名词或代词叫做定语从句的先行词，它与定语从句之间要有一个词连接，这个词指代先行词的内容叫做关系词。
关系代词: _____ _____ _____ ______ _______ as引导非限定性定语从句 关系副词： ______ _______ ______
结构：先行词+关系词+定语从句。
主句从句的成分必须完整；关系代词在从句中作主宾表定, 关系副词做状语。
解题思路：1. 划清主从句，找准先行词；
2. 分析从句中缺少成分
3. 如果缺少主宾表定选择关系代词，如果缺少状语则选择关系副词。
(一) 关系代词引导的定语从句
1. who先行词是 “人” ，在从句中作_______ _________； （多做主语） whom先行词也是人，但在从句中只能作__________； This is the man who helped me. This is the man who/whom you helped.
2. which: 先行词是物，在从句中作_______ _______ This is the book which you are looking for. The building which is being built will be a library.
3. that: 先行词是人或物，在从句中作________ _________ ________。 The lady that came to our school is from America. The book that I just read is very interesting.
She is not the lovely girl that she used to be.
注意：which /who /that 在从句中作宾语可以省略
4. whose: 先行词是人或物，在从句中做_________。一般形式为whose +名词， 相当于the+名词+which/whom，例如：
I live next door to a couple __________ children often make a lot of noise. He has written a book__________ name I have forgotten.
=He has written a book ____ ______ _____ _____ I have forgotten. （二）以下情况只用that 不用which：
(1)anything,nothing,all, any, little, much,few等不定代词作先行词。 (2)先行词被all, much, little, every, no, any等词修饰时,用that。 (3)先行词被the only, the very 修饰。 (4)先行词被形容词最高级或序数词修饰。 (5)先行词既有人又有物时。
1. Is there anything that I can do for you?
2. I have read all the novels that were written by Shakespeare. 3. This is the most wonderful time that I have ever had. 4. What is the first American film that you have seen? 5. This is the very book that he is looking for.
6. Do you know the things and persons that they are talking about? （三）定语从句分为限定性定语从句和非限定性定语从句：
限定性定语从句：从句对先行词进行必要的描述或说明，缺少它，则句义显得不完整，从句与先行词紧密相连。
非限定性定语从句：对先行词进行补充说明，解释，它与先行词之间有逗号隔开，将从句拿掉后其他部分仍可成立，注意：“that”不能够引导非限定性定语从句。 I have a brother who is studying abroad.
Charles Smith, who was my former teacher, retired last year.
非限制性定语从句还能将整个主句作为先行词, 对其进行修饰, 这时从句谓语动词要用第三人称单数。例如：
He was late again, which made his teacher angry.
He seems not to have grasped what I meant, which greatly upsets me. Liquid water changes to vapor, which is called evaporation.
（四）“介词+关系代词”引导的定语从句
1、关系代词在定语从句中作介词宾语，这些关系词在介词后面只能用which 或whom. 不能用that. 也不能用who.
There was a man with whom I would have to work together . The book to which he devoted much time is to come out next month.
2、“介词+关系代词”前还可有some, any, none, all, both, neither, many, most, each, few等代词或者数词。
He loves his parents deeply, _____ _____ _____ 他们俩are very kind to him.
Up to now, he has written ten stories,______ _____ _____ 其中３部are about country life.
（五）关系副词引导的定语从句 when, where, why
1. I’m very glad to return to my hometown ________I had lived for 10 years. 2. This is my hometown _________ I had lived in for 10 years. 3. Do you know the reason ________he is late for school.
4. No one believes the reason________he gave us about his absence at the meeting. 5. I still remember the day _________ I first came to school.
关系副词when, where, why的含义相当于\"介词+ which\"结构，因此常常和\"介词+ which\"结构交替使用，例如：
1.Beijing is the place where (____ _____) I was born. 2.Is this the reason why (____ _____) he refused our offer? 3.This is the house where (____ _____) I lived two years ago. 4.Do you remember the day when (____ _____) you joined our club?
(七) as引导的定语从句
(1) 引导限定性定语从句,可以在从句中做主语，宾语，表语 一般结构为the same… as；such…as ，译为 和……一样……。
We have found such tools as are used in their factory.
I have got into the same trouble as he has. He is not the same man as he was. （2）引导非限制性从句，常带有 _____ 之意。 As we all know, smoking is harmful to one's health. = As is known to all, smoking is harmful to one's health.
as是关系代词。例1中的as作know的宾语；例2中，它充当从句的主语，谓语动词know要
用被动式。
(八）定语从句中的主谓一致
1. Tom is one of my friends that______( love) English very much. 2. Tom is the only one of my friends that_______ (love) English very much.
[定语从句练习]：Practice makes perfect!
1. 定语从句（一）：一、三 2. 定语从句（二）：一、二、三 3. 定语从句（三）：一、二、三、五 4. 定语从句（四）：一、二、三、四
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