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。
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。
6、由when, where, why引导的定语从句，如:
I don't know the reason why he was late。
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。
（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。
扩展资料
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?
参考资料来源：百度百科-定语从句
定语从句，又称为关系从句，顾名思义在句中有着修饰限定的作用，可修饰单一的词（名词或代词），也可修饰一个句子。其中被定语从句修饰的词称为先行词，定语从句由关系词（关系代词或关系副词）引导，被定语从句修饰的词叫作先行词。
关系代词：who, which, who, whom, whose
关系副词：when, where, why, how
关系词的作用：除引导从句外，还代替先行词在从句中充当一定的成分，如主语，宾语，定语，状语等。
1. 关系代词引导的定语从句
1.1 关系代词的作用：
关系代词可以代替指人和物的先行词，在从句起主语，宾语，定语的作用。
A. Where was the man who(that) had made a great progress in studying archaeology.
在研究考古学方面取得伟大成就的人在哪？（who或that 引导的从句在句中作主语）
B.The woman whom(that) you met is our teacher.
你刚才看到的那个女士是我们的老师。（whom或that yin引导的从句在句中作宾语）
C.She had brought these flowers which(that) died at last year.
她买的这些花儿在去年都凋谢了。（which或that引导的从句）
D.Is there someone whose booklet have lost in library.
有谁的手册落在图书馆了吗？（whose引导的从句作定语）
2. 关系副词引导的定语从句
2.1 关系副词的作用
关系副词代替句中的先行词，在句中起时间，地点，原因状语的作用。关系副词有时也相当于介词+which结构
A.The city where(in which) a new building is going to be built.
这座城市将有一个新的建筑被修建。（where引导定语从句修饰the city）
B.He wants to know the reason why(for which)he failed in the game.
他想知道为什么他会在比赛中失败的原因。（why引导定语从句修饰the reason）
C.We arrived there at evening(when)the store closed.
我们在店铺打烊的晚上到了。（when引导定语）
3. 非限定性定语从句
3.1限定性定语从句和非限定性定语从句的区别
限定性定语从句不用逗号和主句分开，是对先行词的补充说明，不能删除。
非限定性定语从句可以用逗号分开，删除以后句子意思完整。例如：
A.He own a house which has a swimming pool, actually.
事实上，他拥有一个有着游泳池的房子。（限定性）
B.He own a house,which has a swimming pool, actually.
事实上，他拥有一个房子，这个房子带有游泳池。（非限定性）
3.AS引导的定语从句
4. as引导非限定性定语从句，可放在主句之前或之后。
A.He is from China,as I know from his accent.
正如我从他的口音得知，他来自中国。
拓展资料
定语 从句由关系词（关系代词、关系副词）引导，关系代词、关系副词位于定语从句句首。
关系代词有：who, whom, whose, that, which等。
关系副词有：when, where, why等。
18.1 关系代词引导的定语从句
关系代词所代替的先行词是人或物的名词或代词，并在句中充当主语、宾语、定语等成分。关系代词在定语从句中作主语时，从句谓语动词的人称和数要和先行词保持一致。
1）who, whom, that
这些词代替的先行词是人的名词或代词，在从句中所起作用如下：
Is he the man who/that wants to see you?
他就是你想见的人吗？（who/that在从句中作主语）
He is the man whom/ that I saw yesterday.
他就是我昨天见的那个人。（whom/that在从句中作宾语）
2) Whose 用来指人或物，(只用作定语, 若指物，它还可以同of which互换）, 例如：
They rushed over to help the man whose car had broken down. 那人车坏了，大家都跑过去帮忙。
Please pass me the book whose (of which) cover is green. 请递给我那本绿皮的书。
3）which, that
它们所代替的先行词是事物的名词或代词，在从句中可作主语、宾语等，例如：
A prosperity which / that had never been seen before appears in the countryside. 农村出现了前所未有的繁荣。（which / that在句中作宾语）
The package (which / that) you are carrying is about to come unwrapped. 你拿的包快散了。(which / that在句中作宾语）
18.2 关系副词引导的定语从句
关系副词可代替的先行词是时间、地点或理由的名词，在从句中作状语。
1）when, where, why
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：
There are occasions when (on which) one must yield. 任何人都有不得不屈服的时候。
Beijing is the place where (in which) I was born. 北京是我的出生地。
Is this the reason why (for which) he refused our offer? 这就是他拒绝我们帮助他的理由吗？
2）that代替关系副词
that可以用于表示时间、地点、方式、理由的名词后取代when, where, why和"介词+ which"引导的定语从句，在口语中that常被省略，例如：
His father died the year (that / when / in which) he was born. 他父亲在他出生那年逝世了。
He is unlikely to find the place (that / where / in which) he lived forty years ago. 他不大可能找到他四十年前居住过的地方。
18.3 判断关系代词与关系副词
方法一： 用关系代词，还是关系副词完全取决于从句中的谓语动词。及物动词后面无宾语，就必须要求用关系代词；而不及物动词则要求用关系副词。例如：
This is the mountain village where I stayed last year.
I'll never forget the days when I worked together with you.
判断改错（注：先显示题，再显示答案，横线；用不同的颜色表示出。）
（错） This is the mountain village where I visited last year.
（错） I will never forget the days when I spent in the countryside.
（对） This is the mountain village (which) I visited last year.
（对） I'll never forget the days (which) I spent in the countryside.
习惯上总把表地点或时间的名词与关系副词 where, when联系在一起。此两题错在关系词的误用上。
方法二： 准确判断先行词在定语从句中的成分(主、谓、宾、定、状)，也能正确选择出关系代词/关系副词。
例1. Is this museum ___ you visited a few days age?
A. where B. that C. on which D. the one
例2. Is this the museum ____ the exhibition was held.
A. where B. that C. on which D. the one
答案：例1 D，例2 A
例1变为肯定句： This museum is ___ you visited a few days ago.
例2变为肯定句： This is the museum ___ the exhibition was held.
在句1中，所缺部分为宾语，而where, that, on which都不能起到宾语的作用，只有the one既做了主句的表语，又可做从句的宾语，可以省略关系代词，所以应选D。
而句2中, 主、谓、宾俱全，从句部分为句子的状语表地点，既可用副词where，又因 in the museum词组，可用介词in + which 引导地点状语。而此题中，介词on 用的不对，所以选A。
关系词的选择依据在从句中所做的成分，先行词在从句中做主、定、宾语时，选择关系代词 (who, whom, that, which, whose)； 先行词在从句中做状语时，应选择关系副词 ( where 地点状语，when 时间状语，why 原因状语) 。
18.4 限制性和非限制性定语从句
1) 定语从句有限制性和非限制性两种。限制性定语从句是先行词不可缺少的部分，去掉它主句意思往往不明确；非限制性定语从句是先行词的附加说明，去掉了也不会影响主句的意思，它与主句之间通常用逗号分开，例如：
This is the house which we bought last month. 这是我们上个月买的那幢房子。（限制性）
The house, which we bought last month, is very nice.这幢房子很漂亮，是我们上个月买的。（非限制性）
2) 当先行词是专有名词或物主代词和指示代词所修饰时，其后的定语从句通常是非限制性的，例如：
Charles Smith, who was my former teacher, retired last year. 查理·史密斯去年退休了，他曾经是我的老师。
My house, which I bought last year, has got a lovely garden. 我去年买的的那幢房子带着个漂亮的花园。
This novel, which I have read three times, is very touching. 这本小说很动人，我已经读了三遍。
3) 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 seems not to have grasped what I meant, which greatly upsets me. 他似乎没抓住我的意思，这使我心烦。
Liquid water changes to vapor, which is called evaporation. 液态水变为蒸汽，这就叫做蒸发。
说明：关系代词that和关系副词why不能引导非限制性定语从句。
18.5 介词+关系词
1）介词后面的关系词不能省略。
2）that前不能有介词。
3） 某些在从句中充当时间，地点或原因状语的"介词+关系词"结构可以同关系副词when 和where 互换。
This is the house in which I lived two years ago.
This is the house where I lived two years ago.
Do you remember the day on which you joined our club?
Do you remember the day when you joined our club?
18.6 as, which 非限定性定语从句
由as, which 引导的非限定性定语从句，as和which可代整个主句，相当于and this或and that。As一般放在句首，which在句中。
As we know, smoking is harmful to one's health.
The sun heats the earth, which is very important to us.
典型例题
1）Alice received an invitation from her boss, ___came as a surprise.
A. it B. that C. which D. he
答案C. 此为非限定性从句，不能用 that修饰，而用which.，it 和he 都使后句成为句子，两个独立的句子不能单以逗号连接。况且选he句意不通。
2）The weather turned out to be very good, ___ was more than we could expect.
A. what B. which C. that D. it
答案B。which可代替句子，用于非限定性定语从句，而what不可。That 不能用于非限定性定语从句，it不为连词，使由逗号连接的两个句子并在一起在英语语法上行不通。
3）It rained hard yesterday, ____ prevented me from going to the park..
A. that B. which C. as D. it
答案B.
as 和which在引导非限制性定语从句时，这两个关系代词都指主句所表达的整个意思，且在定语从句中都可以作主语和宾语。但不同之处主要有两点：
(1） as 引导的定语从句可置于句首，而which不可。
(2） as 代表前面的整个主句并在从句中作主语时，从句中的谓语必须是系动词；若为行为动词，则从句中的关系代词只能用which.。
在本题中，prevent由于是行为动词，所以正确选项应为B。
As 的用法
例1. the same… as；such…as 中的as 是一种固定结构, 和……一样……。
I have got into the same trouble as he (has).
例2. as可引导非限制性从句，常带有'正如'。
As we know, smoking is harmful to one's health.
As is know, 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。
18.7 先行词和关系词二合一
1)Whoever spits in public will be punished here.
(Whoever 可以用 anyone who 代替)
2)The parents will use what they have to send their son to technical school.
(what 可以用all that代替)
18.8 what/whatever;that/what; who/whoever
1）what = the thing which；whatever = anything
What you want has been sent here.
Whatever you want makes no difference to me.
2) who= the person that whoever= anyone who
（错）Who breaks the law will be punished.
（错）Whoever robbed the bank is not clear.
（对）Whoever breaks the law will be punished.
（对）Who robbed the bank is not clear.
3) that 和 what
当that引导定语从句时 ，通常用作关系代词，而引导名词性从句时，是个不充当任何成分的连接词。宾语从句和表语从句中的that常可省略。What只能引导名词性从 句， 用作连接代词，作从句的具体成分，且不能省略。
I think (that) you will like the stamps.
What we need is more practice.
18.9 关系代词that 的用法
1）不用that的情况
a) 在引导非限定性定语从句时。
(错) The tree, that is four hundred years old, is very famous here.
b) 介词后不能用。
We depend on the land from which we get our food.
We depend on the land that/which we get our food from.
2) 只能用that作为定语从句的关系代词的情况
a) 在there be 句型中，只用that，不用which。
b) 在不定代词，如：anything, nothing, the one, all, much, few, any, little等作先行词时，只用that，不用which。
c) 先行词有the only, the very修饰时，只用that。
d) 先行词为序数词、数词、形容词最高级时，只用that。.
e) 先行词既有人，又有物时。
举例：
All that is needed is a supply of oil.
所需的只是供油问题。
Finally, the thief handed everything that he had stolen to the police.
那贼最终把偷的全部东西交给了警察。
这些全在这了 够了吧？本回答被提问者和网友采纳
Is he the man who wants to see you?
这个句子中的who wants to see you就是定语从句。who是关系代词，在从句中作主语。
She is the woman whom I saw yesterday.
关系代词whom在定语从句whom I saw yesterday 中作宾语，因为正常语序是I saw +人(whom) yesterday，定语从句里把whom提前，作为关系代词引导整个从句。
你可以把定语从句看成是一个以句子形式出现的定语，在第一个句子中定语修饰的是the man，定语（从句）是对the man进行解释说明：那个想见你的（who wants to see you）男人(the man)，翻译成中文时把英语中的定语部分放到“男人”的前面，这样才符合汉语表达习惯。
关系代词除了who,whom以外，还有whose,which,that.
Please pass me the book whose cover is green.请递给我那本绿色封面的书。
The package which/that you are carrying is about to come unwrapped.你拿的包快散了。
除了关系代词可以引导定语从句外，关系副词也可以引导定语从句。关系副词有when,where,why.
Nanjing is the place where I was born.南京是我的出生地。
关系副词where=in which,所以这句话也可以这样说：Nanjing is the place in which I was born.
短语Be born in + 地方，要把born 后面的介词in提前放到which的前面。
什么时候用关系代词，什么时候用关系副词呢？
当从句中的及物动词后面没有宾语时，要用关系代词引导从句。
This is the city which I visited last year.
及物动词visit后面没有宾语，要用关系代词which引导定语从句。
当先行词在从句中做主语，定语，宾语时，要用关系代词引导从句；当先行词在从句中做状语时，要用关系副词引导从句。
Is this the village which you visited a few days ago?
You visited the village a few days ago,所以先行词village在从句中是做宾语,要用关系代词which引导从句。
Is this the museum where the exhibition was held?
The exhibition was held in the museum,所以先行词in the museum在从句中是做地点状语（表示地点），要用关系副词where引导从句（where=in which)。
关系代词who指人，which指物；that用在限定性定语从句中，又可以指人又可以指物。
限定性定语从句不能被省略，如果被省略了，就会影响整个句子的理解；非限定性定语从句起补充说明的作用，即使被省略了，也不会影响全句的理解。
and的用法
1. 连接两个相同的比较级，表示“越来越……”。如：
It moves faster and
faster. 它动得越来越快。
Your work is getting better and better.
你的工作干得越来越好了。
2. 连接两个相同的动词，表示动作的反复或连续。如：
He coughed and coughed.
他咳个不停。
He tried and tried but without success. 他试了又试，但没有成功。
3.
连接两个相同的名词，表示“许多”或“有各种各样的” (即有好的也有坏的)。如：
They talked for hours and hours.
他们谈了很长时间。
There are books and books. 有各种各样的书(即书有好坏之分)。
定语从句中which和that的用法区别
定语从句只能用that 的几种情况
1．当先行词是anything, everything, nothing (something 除外), few, all, none, little, some 等代词时，
Have you taken down everything that Mr. Li has said?
2. 当先行词被序数词修饰
(1) The first place that they visited in London was the Big Ben.
3. 当先行词被形容词最高级修饰时
(1) This is the best film that I have seen.
4. 当形容词被the very, the only修饰时
(1) This is the very dictionar5. 当先行词前面有who, which等疑问代词时
(1) Who is the man that is standing there?
(2) Which is the T-shirt that fits me most?
6. 当先行词既有人，也有动物或者物体时
(1) Can you remember the scientist and his theory that we have lear只能用which
在介词后面的关系代词用which而不能用that。即“介词+which（代物）”
1.The picture for which he paid $1,000 was once owned by a duke.
【他花了1000美元买下的画曾为一名公爵所拥有。】