定语从句
复合句中修饰名词或代词的从句，叫做定语从句。被定语从句修饰的词叫先行词，定语从句必须放在先行词之后。
引导定语从句的关系代词有： that,which, who(宾格 whom,所有格 whose) 和关系副词when, where 和 why。关系代词和关系副词有两个作：一是把主句和从句连接起来；二是在从句中作一个句子成分，关系代词可作主语、宾语、定语，关系副词可作状语。
例如： There are plants which have neither roots nor leaves.（有些植物既无根又无叶。）（句中 which have neither roots nor leaves 定语从句，修饰先行词 plants。关系代词which引出定语从句同时在从句中作主语。）
根据与先行词的关系，定语从句可分为限制性定语从句和非限制性定语从句。
一、限制性定语从句
限制性定语从句限制或规定先行词的范围，和先行词有着不可分割的关系，对于全句的意义来说是不可缺少的。如果去掉定语从句，全句的意义就不明确、不完整。
如： That is the man who gave us a report yesterday. 那就是昨天给我们作报告的人。
（一）引导限制性定语从句的关系代词
这些词有 who, whom, whose, that, which。关系代词既代表先行词，又在从句中担任一种句子成分，如主语、宾语、表语或定语。关系代词的用法见下表：
1. who 代表人，在从句中作主语
The boy who delivers newspapers is my brother.送报纸的那个男孩是我的弟弟。
you are the only person here who knows me. 你是这里唯一认识我的人。
He was the man who bought my car. 他就是买了我的车那个人。
2 .whom 也代表人，有时可以省略。
Many people (whom) we know are concerned about air pollution. 我们认识的许多人关心空气污染问题。
注：
（1）在口语中，有时可以用who 来代替 whom, 并可以省略。
如： The worker (whom/who) you mentioned has not come. who 来代替 whom, 并可以省略。（2）在介词后．只能用 whom, 不能省略。
如： The boy about whom you talked has gone home.
The boy (whom/who) you talked about has gone home.
（你谈到的那个男孩已经回家了。）
3. whose 代表“某人或某物的 "' 在从句中作定语。
The woman whose bike was stolen is John’s teacher. 自行车被盗的那个妇女是约翰的老师。
I just bought the magazine whose format is similar to that of yours.我刚买了版式和你的相似的杂志。
4.which 代表物，在从句中可作主语，也可作宾语。
We often use the ladder which is made of wood 我们常常使用木头做的梯子。
They like the trees( which) they planted. 他们喜欢他们栽的树。
注：当 which 作宾语时 , 可以省略；但是在介词后，which 不能省略。
This is the book about which I told you last week.
This is the book which I told you about last week. 这就是我上星期告诉你们的那本书。
5.that 既可代表人，又可代表物。
The girls (that) he interviewed were always complaining about their long hours. 他访问的那些姑娘总是抱怨工作时间长。
The directions that were given to John were easy to follow. 给约翰的那些指示很容易执行。that 常常可以代替 who, whom和 whose。
The man that told you the news will come here this afternoon. 告诉你那个消息的人今天下午要
到这里来。
He is the man (that) I saw in your room yesterday afternoon. 他就是昨天下午我在你房间里见
到的那个人。
This is the book (that) I like best. 这是我最喜欢的书。
注：在介词后不能用 that; 当先行词为 everybody,anybody,everyone, anyone 等时要用who, 不能用that; 当先行词前有数词、形容词最高级或all, any, no, only ,little, very ,much 等词时，或先行词本身为all , little, much ,anything, something, nothing等词时，要用that, 不用which.
Is there anyone who can answer this question? 有人能回答这个问题吗？
He is the tallest man that has ever lived here. 他是在这里住的个子最高的人。
There is nothing that can be done now. 现在没有什么事情可做了。
The first English novel that I read was Atale of Two Cities by Charles Dickens. 我读的第一本英
文小说是狄更斯写的《双城记》。
（二）引导限制性定语从句的关系副词
这些词有where, when,why 。关系副词在从句中作状语，意义上相当于“介词＋关系代词”。l. wbere 修饰表示地点的名词，在从句中充当地点状语，意义上相当于一个介词加Which （或on which , in which 等）
He is going to viisit the city where (= in which) he was born. 他打算去访问他出生的那个城市。The office where (= in which) he works is on the second floor. 他工作的办公室在二楼。
The house where (= in which) I used to live has been pulled down 我过去曾住过的那所房子已
被拆掉了
2.when修饰表示时间的名词，在从句中充当时间状语，意义上相当于一个介词加 Which (=on which, in which 等）
如：The day when (= on which) they moved into their new home was bright and sunny 他们迁
入新居那一天阳光灿烂。
April is the month when(= in which) we have a lot of rain. 四月是个多雨的月份。
3.why 通常修饰名词 reason ( 理由，原因），在从句中充当原因状语，意义上相当于 for Which 。
Th is is the reason why(= for which) I am leaving tomorrow 这就是我明天要离开的原因。
The reason why (= for which) he left the room is quite obvious 他离开房间的原因是很明显的。The reason why (= for which) he committed suicide is unknown他为什么自杀无人知晓。
二、非限制性定语从句
非限制性定语从句是对先行词作进一步的说明，与先行词的关系比较松散，如果去
掉定语从句，主句仍然成立。在书面语中，通常用逗号把从句和主句隔开。
