定语从句
什么叫定语从句？要了解定语从句，得先从定语说起。我们在初中的时候学过定语。定语就是用来修饰名词或代词的成分。比如形容词（good school, tall boy, important meeting, Chine food, etc），名词 (wood table，book shelf, etc)代词(my mother, this text, some trees，etc), 数词(one country，etc), 副词(the roads here，etc), 介词短语(the newspapers in English, a report on DNA, etc) 以及不定式(the work to do，etc),分词(the smiling girl)。
找出下面句子中的定语.
1. Mary likes English songs. 2. There is much water.
3. I don’t know the parks here. 4. They are talking about the tiger in the cage
5 . Here is a good book for you to read.
定语从句就是用来修饰前面的名词或代词的句子，也就是说用来做定语的句子。又因为做定语的多是形容词，所以，定语从句又被称为形容词性从句。
●知识过渡精讲
一、基本概念
1. 先行词和主句
当句子中的某个名词或代词的后面带有定语从句的时候，这个名词就叫先行词；先行词所在的句子就是主句；先行词后面起修饰作用的句子是定语从句
2. 定语从句的位置---------要放在名词后面。
3. 关系词
我们不能直接把一个句子放在某个名词的后面. 我们还必须在这个定语从句的前面加一个关系词。关系词又分为关系代词(who, whom, who, which, that,)和关系副词(where, when, why)
4. 限制性定语从句和非限制性定语从句
限制性定语从句：是句中不可缺少的组成部分，它用来确定先行词的身份，即所指的是哪些人或物。如果没有了这个定语从句，先行词的意思就不明确，主句也不完整。如：
The hou which Sue has bought is over 100 years old.
非限制性定语从句：是先行词的补充说明，它不能告诉我们讲话者指的是哪一个人或物，而是提供更多的有关所谈论对象的情况。没有它不会影响主句意思的明确或完整。一般用逗号分开先行词和从句。例如：
Sue’s hou, which is in the center of the town, is over 100 years old.
二、掌握定语从句的关键是正确使用关系词，下面我们将向同学们常见的关系词以及他们的主要用法：
1. 关系词
（1）that: 多指物，也可指人。在从句中作主语，宾语，偶尔做表语或状语。如:
The factory that produced bikes is very big. （ 作主语）
The letter that I received was from my son.（作宾语）
He is not the man that he was.（作表语）
I don’t like the way that you speak to me. （作状语）
注意：当谈及关系词所作成分时，均是指其在定语从句中的功能，与主句无关，这是初学者常常忽略的。
（2）which用于指物，在从句中作主语或宾语，如：
The keys which were missing have been found.（作主语）
The books which I bought yesterday are on medicine. ( 作宾语)
注意：指物时that和which可互换,但下面几种情况通常用that引导定语从句,不能用which
1. 当先行词有最高级修饰或本身就是最高级时. 如:
This book is the most difficult one that I have ever read.
The best that I could do was to keep silent .
2. 当先行词有序数词修饰或本身就是序数词时.如:
Here are two workers, the third that you want is to come in a minute.
The cond school that I visited here was a private school.
3. 当先行词是 all, something, anything, little, much, none等不定代词时.如:
All that I need is more time.
There is little that I can do to make up for the lost time.
4. 当先行词有the only, all, the very, no等词修饰时.如:
There are no people that like to be laughed.
The only thing that they could do was to wait.
It is the very place that a ver accident happened yesterday.
5. 当先行词既有人又有物时. 如:
They talked about the things and persons that they remembered .
The man and the manners that he describes in his book are true.
6. 在以who开头的疑问句中，如：
Who is the boy that is sitting at the gate?
Who was she that he danced with?
注意：下面几种情况通常用which来引导定语从句，而不用that
①．关系代词在介词后面时,如：
This is the chair on which I sat just now.
This is the room in which we lived .
如果要用that引导从句，则介词不能放在that前面，只能放在从句中相应动词的后面。
比如上面的句子也可以说成：
This is the chair that I sat on just now
在含有介词的固定动词短语中，介词不能提前，如：
That is the man that she has been looking after.（look after 为固定短语，意为：照顾）
不能写成：
That is the man after whom she has been looking 。
②．在非限制性定语从句中。如：
They are hollow, which makes them very light.
The book, which was written in 1994, was published in 1996.
③．先行词为that时，如：
What’s that which you are looking at?
What’s that which you are holding in your hand?
(3). who 指人，在从句中作主语。（现在语法要求宽泛了，有时也可用在从句中作宾语）
Here is the doctor who worked in the hospital fighting against SARS.
(4).whom 指人，在从句中作宾语。
The teacher whom you want to e is coming soon.
(5).who 既可指人也可指物。在从句中作定语。
The girl who father is a worker is good at maths.( 指人)
The little hou who windows face south is mine.（指物）
2．关系副词
(1).when 指时间，在从句中作时间状语
I’ll never forget the day when I got a prent from my father.
我永远都不会忘记父亲给我礼物的那一天。（其中先行词在从句作我收到礼物的时间状语，所以这个定语从句用when来引导。）
(2). where 指地点，在从句中作地点状语。
The place where I work is far from here.
我工作的地方离这里很远。（其中先行词地方在从句中作我工作的地点状语，所以从句用where引导。）
Is there a shop around where I can buy a tin Coca-Cola?
(3). why 指原因，在从句中作原因状语。
don’t know the reason why he didn’t come to the meeting.
我不知道他没来开会的原因。（其中先行词原因在从句中作他没来开会的原因状语，所以从句用why引导）
注意： “ as ” 也可用来引导定语从句，如，当先行词有the same或such修饰时
They talked of the same man as you met in a faraway village.
I have never en such an old tree as they found in front of the temple.
