一、定语从句与引导词
　　定语从句是在复合句中修饰某一名词或代词的从句。被修饰的名词或代词叫做选行词， 而引导定语从句的词叫引导词，有关系代词和关系副词两类。
懂得什么样的先行词后用什么样的引导词是学好定语从句的关键。
1．关系代词有：that, which, who, whom, whose在定语从句中作主语、宾语中表语，whose作定语。代人的有：who, whom, whose, that；代物的有：that, which, whose. 例如：
　　The man who helped you is Mr White.(who代人，在定语从句中作主语)
　　That is the person (whom/who/that) you want to see.(whom, who, that代人，在定语从句中作宾语，可省略)
　　I'm not the fool (that) you thought me to be.(that代人，在定从中作表语)
　　A dictionary is a useful book which(＝that) tells us the meaning of words(which或that代物，在定从中作主语)例如：
2 ．关系副词有：when(指时间)，where(指地点)，why(指原因)，在定语从句中作状语。
　　Would you suggest a time　(when) we can have a talk?(when可省略)
　　The house where they live is not very large./This is the reason why he did not came to the meeting.
　　注意：不是表时间的先行词都用when引导定从，不是表地点的先行词都用where引导定从。例如：
　　　We'll visit the factory which (＝that) makes radios.
　　　（which或that在定从中作主语，where不可用主语，故不可用）
　　　They still remember the happy days (which/that) they spent in Beidaihe.
　　　 （which或that在定从中作spent的宾语，when不可作宾语，故不可用）


二、限制性定语从句与非限制性定语从句
1．限制性定语从句
先行词
关联词
例句
说明
人
在从句中做主语或宾语
who

This is the doctor who saved the boy's life .
这就是救了孩子生命的医生。
She is the new student whom I want to introduce to you.
她就是我要介绍给你的新学生。

who在从句中做主语
whom在从句中做宾语，口语中who可以代替whom，也可以被省去，但做介词宾语时只能用whom。

物

在从句中做主语或宾语
which

Please pass me the book which is lying on the table.
请递给我摆在桌上的那本书。
The novel which Tom bought is very interesting.
汤姆买的小说很有意思。
Can you lend me the magazine about which you talked yesterday?
你能把昨天谈到的那本杂志借给我吗？

which在从句中做主语。
which充当宾语时可以省去。

 

which做介词宾语不可省。

人或物的
whose

The professor whose daughter teaches you English is Dr. Williams
那位教授是威廉斯他的女儿教你英语。
= The professor, the daughter of whom teaches you English is Dr. Williams.
The bike whose brake was damaged has now been repaired.
那辆坏了闸的自行车现在已经修好了。
=The bike the brake of which was damaged has now been repaired.

whose在从句中做定语
指某人的也可以用... of whom代替whose
指物时也可以用... of which 代替 whose

all, little much和some,any every,no 构成的合成代词

that

They talked for about an hour of things and persons that they remember in the school.
他们谈起他们所记得起的学校里的人和事，谈了大约有半个小时。
I'll tell you all(that)I know about it .
我要告诉你我所知道这件事的一切情况。
Is there anything (that) I can do for you?
有什么我可以帮助做的事吗？
I've brought everything (that )you need.
我把你需要的东西都拿来了。

先行词分别表示人和物，关系代词要用that，不用who或which先行词表示物，关系代词用that不用which，在从句中做宾语可省去。如果先行词是人时，关系代词不受制约，用that或who (whom)均可。
人或物
that

This is the best film that I have seen .
这是我看过的最好的一部电影。
The first place that we'll visit is Beijing Library.
我们要参观的第一个地方是北京图书馆。

 先行词被形容词最高级或序数词修饰时定语从句用that引导。

He is the only person that is believable.
他是唯一可靠的人。
John is the very person that she wants to see.
约翰正是她要见的人。

先行词被the only, the very, the same 等修饰时用关系代词that.

Who is the man that is talking with Tom?
正在和汤姆谈话的人是谁？
Which of the books that you bought is easy to read?
你买的那些书中哪一本容易读。

 当主句以who、which开头的特殊疑问句时，定语从句要用that。
时间

when

He came at a time when we. needed him most.
他在我们最需要的时候来了。
We'll never forget the day when the People's Republic of China was founded.
我们永远不会忘记中华人民共和国成立的那一天。

 在定语从句中作时间状语。
注：先行词是time, minute, moment, next time很少用关系副词when，可用that 但通常省去。
地点

where

This is the room where he put up for the night.
这就是他度过夜晚的那房子。

 在定语从句中作地点状语
原因理由

why

I know the reason why she studies so well.
我知道她学习好的原因。

 在定语从句中作原因状语


2．非限制性定语从句
先行词
关联词
例句
说明
人
who
whom

George, who is my classmate, has won a scholarship.
乔治获得了奖学金，他是我的同学。
Dr. Li, whom I know very well, will come here tomorrow.
李大夫明天将来这儿，我跟他很熟悉。

who, whom不能省去，也不能用that代替。

物
which

I gave him a New Year card, which he enjoyed very much.
我给他一张贺年卡，他很喜欢它

which指物，不可省去，也不能用that代替。

没有固定的先行词而是一个句子

 
which

He studies hard at school when he was young, which leads to his success in his later life.
他年轻时在校学习努力，这导致了他后来生活中的成功。

which作主语指它前面的整个句子，不可用that代替，强调结果。
as

 

 

 

He gets up early, as is always his habit.
他总是早起床，这是他的习惯。

as指全句，在从句中做主语。

John was admitted into the college, as we had expected.
约翰被大学录取了，这是我们期待的。

 as指全句意思，在从句中做宾语。

The earth, as is known to all, is round.
人人皆知，地球是圆的。

as引导的定语从句可以放在句首，句中或句末。

Who is the man that is talking with Tom?
正在和汤姆谈话的人是谁？
Which of the books that you bought is easy to read?
你买的那些书中哪一本容易读。

 当主句以who、which开头的特殊疑问句时，定语从句要用that。

This is the same book as I lost yesterday.
这本书与我昨天丢失的那本书一样。

 用于the same...as, such...as, as...as等结构中。


三、只用that引导和不用that引导的场合
1．只用that引导
1）当先行词既包括人又包括物时：He talked about the men and the books that attracted him.
2）指物的先行词被any, every, only, very, all, no等修饰时：These are the very points that interest me. / That's the only watch that I like most.
3）指物的先行词被序数词或形容词最高级修饰时：The first step that we are to take is very difficult. / This is the second card that he gave me.
4）先行词是指物的不定代词all, little, few, much及everything, anything, nothing等时：There is still much that can be done about it./Have you got everything that you need?
5）先行词是who时：Who that have seen him does not like him?

2．不用that的场合如下：
1）非限制性定语从句中Last night, I saw a very good film, which was about the Long March .
2）介词放在关系代词之前时 This is the man from whom I learnt the news.
3）句中出现了that，或先行词是that时 I have found that which I was looking for.

四、“介词＋关系代词”用法
1．介词的确定应依据定语从句中短语的习惯性搭配，例如：
　　 Who is the girl with whom you just shook hands?（shake hands with...是习惯性搭配）
2．介词常受先行词的制约（即介词和先行词的搭配），例如：
　　 He built a telescope through which he could study the skies.（through which 即through the telescope）
3．当关系代词作“动词＋介词”固定短语的宾语时，此时因定短语中的介词不能拆开移到关系代词前。例如：
　　 This is the watch which you're looking for./He is a kind of man whom you can safely depend on.

五、几个名词后的引导词
1．situation后常用where, in which引导定语从句：
　　 Can you imagine a situation where/in which you can use the word?
2．way （方式，方法）后常用in which或that或how引导定语从句，也可省略：
　　 Do you know the way (in which / that / how) he worked out the problem?
3．“the same＋名词”，“such＋名词”，“as＋名词”后通常用as引导定语从句。
　　例如：I have the same dictionary as you (have). /Such a book as you bought is not worth buying.