定语可以由形容词、名词、代词、分词、不定式以及介词短语等来担任，也可以由一个句子来充当，充当定语功能的句子称为定语从句。定语从句“三要素”
1.先行词：被定语从句所修饰的名词或代词①指人的先行词②指物的先行词★ 先行词还可以是前面整个句子所叙述的事情。He has passed the driving test, which surprises all of us. (which替代前面所叙述的事情) 先行词
2.关系词：引导定语的词(1)关系词的作用①替代前面的先行词（替代作用）②连接主句和定语从句（连接作用）③在定语从句中作句子成分（成分作用）(2)关系词的分类①标准：根据关系词在从句中做的句子成分种类②关系代词：在从句中做 主，宾，表，定（
that/which/who/whom/whose/as）③关系副词：在从句中作状语(When/where/why)
3.定语从句：用来做定语，修饰限定先行词的句子定语从句的分类
1.限制性定语从句：对先行词起限定修饰作用。He is a teacher who works at our school.
2.非限制性定语从句：对先行词起补充说明作用(先行词与定语从句之间有逗号隔开)Beijing, which is the capital of China, is a beautiful city with a long history.比较：He has two sons, who work in the same company. (He has only two sons.)He has two sons who work in the same company. (Perhaps he has two more sons)定语从句的10个难点
1.关系代词的省略(限定性定语从句)
(1)关系代词在定语从句中作宾语
She is the girl (whom / that) I loved before. (可以省略whom/that)
(2)关系代词在定语从句中作表语He is no longer the boy (that) he used to be. (可以省略that)
(3)关系代词作介词宾语，介词在从句句尾时可以省略Housing price is a problem (that/which) people are interested in.比较：Housing price is a problem in which people are interested.（此时只能用which且不能省略）
2.先行词是人(that/who的区别)
(1)用that的情况①以疑问词who开头的句子中Who is the man that is shouting there?②关系代词在从句中作表语时She is not the girl that she used to be.③先行词被the very, the right, the only修饰This is the very person that we are looking for.
(2)用who的情况①先行词是one, ones, anybody, all, none, those 等Those who want to go to the cinema will have to wait at the gate of the school.②句子中有两个定语从句,一个用了that,另外一个用whoWho is the boy that won the gold medal?③在there be 结构中There are many young men who are against him.④在非限定性定语从句当中Tom, who is my best friend, has gone abroad to study.
3.先行词是物(that / which的区别)
(1)用which的情况①在非限定性定语从句中She lost the game, which depressed her greatly.②关系词置于介词之后，作宾语The pen with which you write is Jack’s.③先行词是that或定语从句中套定语从句,一个关系词用that,另一个用which.Let me show you the novel that I borrowed from the library which is newly open to us.
(2)用that的情况①先行词是不定代词如all, little, few, much,anything, everything, nothing, none, no one等She did all that she could to help us.②先行词被all, every, no, some, little, much, the only, he very, the right，the last等所修饰时This is the very book that I want.③先行词中既有人又有物时She described in her compositions the people and he places that impressed her most.④先行词前有序数词或形容词最高级修饰时This is the best book that I have ever read.This is the first film that I’ve seen since I came here.⑤定语从句中套定语从句，其中一个关系词以用which, 另外一个用thatHe built a factory which produced things that had never been seen before.⑥当主句的主语是疑问词which,另一个用thatWho is the person that is standing at the gate?
4.As引导定语从句用法
(1)As 既可以引导限制性定语从句也可以用于非限定性定句中充当主语，宾语，表语等。 常用于以下句型当中：Such/so….. as…. 像…..一样 the same …. as… 和…...同样的A computer is so useful a machine as we can use everyday.He is not the same man as he was.
(2)引导非限制性定语从句，此时译为“正如，像”等。可以放在句首，句中或句末。As I remember, there were a net bar here.Taiwan is an inseparable part of China, as is known to all.★the same as...和the same that...引导定语从句的区别This is the same bike that I lost yesterday. (同一事物)This is the same bike as I lost yesterday. （同类事物）
5.关系副词的运用
(1)When 在定语从句中做时间状语，先行词为表示时间的time, day等
I still remember the day when I first came to Beijing. (when=on which)
(2)Where 在定语从句中做地点状语，先行词为表地点的place, spot等Can you tell me the office where he works? (where = in which)
(3)Why 在定语从句中做原因状语，先行词只有reason.I don’t want to listen to any reason why you were absent. (why = for which)
★ 关系副词 = 相应的介词 关系代词★
Where引导的定语从句还可以修饰抽象空间的名词如case(情形)，situation, position(位置),stage (阶段)，point（地步）等What are the situations where body language is the only form of communication?在哪些情况下身体语言是唯一的沟通方式。(此时where = in which)
6.几个特殊的先行词
(1)way在定语从句中做状语时的三种引导方式 that / in which / 不填The way in which / that / 不填 he explains the sentence to us is quite simple.比较：The way which /that/不填 he told to us was quite simple.★way在定语中作tell的宾语
(2)先行词timetime表示“次数”时，用关系代词that引导定语从句This is the first time that the president has visited the country.time作“一段时间” 讲时，应用关系副词whenThis was the time when there were no radios, no telephones or no TV sets★此时when = during which 在..期间
(3)先行词reason当在定语从句中作状语时，定语从句的4种引导方式 why/for which/that/不填This is the reason why/for which/that/不填 he can not come here.比较：Is this the reason that/which/不填he explained to us for his absence from the conference.★reason 在定语从句中做explain的宾语
7.介词 关系代词
★该结构的关系代词只有两种即 介词 which（指物） 介词 whom（指人）★该结构介词的选用原则：
(1)根据定语从句中谓语动词的习惯搭配This is the book on which I spent $ 8.This is the book for which I paid $
(2)根据先行词的搭配习惯I remember the days during which I lived there.I remember the day on which I graduated from university.
(3)根据整个句子所表达的意思来决定The colorless gas without which we can’t live is called oxygen.
(4)英语中为了强调某一名词，不定式前面也可以加上关系代词。Here is the money with which to buy the piano.She is the right person on whom to depend
注意：①如果介词后移，关系代词可以省略The person (whom/who/that) you will write to is Todd.②有些含有介词的动词短语介词不能提前如look for/after; take care of; send for; hear from/of/about deal with等This is the baby that you will look after.
8.定语从句的主谓一致
(1)当先行词是 one of 复数名词，定语从句的位于动词要用复数形式The Great Wall is one of the world-famous buildings that draw lots of visitor every year.
(2)当先行词是 the only one of 复数名词，从句谓语用单数形式The Great Wall is the only one of the buildings on the earth that is seen from the moon.
(3)先行词如果是整个句子，定语从句的谓语动词用单数Great changes have taken place in China, as is known to all.He has passed the driving test, which surprises all of us.
9.定语从句的转化
定语从句可以转换为 –ing或-ed形式The girl (who is) dancing now just returned from Taiwan.I love the stories (which were) written by Hemingway.The man (who stands) standing there is my friend.
10. 定语从句的解题方法
(1)判断从句是否为定语从句 （先行词，关系词，定语从句）
(2)准确判断先行词在定语从句中的成分(主、宾、表、定、状)从而正确选定使用关系代词或关系副词
注意：①关系代词whose的用法。Whose在定语从句中做定语。当先行词是人：whose = the 名词 of whom 当先行词是物：whose = the 名词 of whichDo you know the boy whose parents / the parents of whom are on holiday?I’d like a room whose window / the window of which faces the sea.②That引导定语从句，名词性从句 和 强调句型的区别:定语从句中的that: 关系代词，在后面的定语从句中做句子成分。名词性从句中的that：从属连词，只起连接主从句的作用，在从句中不做句子成分。强调句中的that, 运用于it is/was…that..结构；判断标准：去掉强调句型结构，成分仍然完整。
比较：This is the book that I am looking for. (that 引导定语从句)It is at Bashu middle school that I have studied for three years. (that和前面的it is构成强调句型)The fact that he stole the money surprised all of us.(that 引导名词性从句--同位语从句)That he will come to the conference has excited all of us.(that引导名词性从句--主语从句)We all expect that they win, for members of their team are stronger.(that引导名词性从句--宾语从句)The reason for your failure is that you lack confidence in yourself.(that 引导名词性从句--表语从句)
