在复合句中，修饰某一名词或代词的从句叫做定语从句。定语从句所修饰的词叫做先行词。定语从句放在先行词的后面。引导定语从句的词叫做关系代词(that, which, who, whom, whose)或关系副词(when, where)，关系代词和关系副词放在先行词与定语从句之间，起联系的作用，同时又作定语从句的一个成分。

关系代词、副词 作用 先行词 例句

that， who，

whom(只做宾语) 主语、宾

语、表语 人 Do you know the girl who/that is standing under a tree?你知道站在树下的女孩是谁吗?

that，which 主语、宾语、表语 物、时

间、地点、原

因

She got a computer which/that her parents bought for her.

她有一台她的父母买给她的电脑。

whose

定语

人物

The boy whose father is a doctor studies very hard.他的爸爸是医生的男孩学习非常刻苦。

The classroom whose window is open is mine.窗户开着的那个教室是我的教室。

when

状语 时间 I still remember the day when you leave for Beijing.我仍然记得你去北京的那一天。

where 状语 地点

This is the school where my mother works.这就是我妈妈

工作的学校。

why

状语

原因

Could you explain the reason why you were late?你能解释一下你迟到的原因吗? 二、关系代词在定语从句中的用法(关系代词作宾语时可省略)：

1.that指人或物，在定语从句中可作主语或宾语。

This is the pen that you are looking for. 这是你要找的那支钢笔。(宾语)

The girl that has long hair is my sister.留着长发的那个女孩是我妹妹。(主语)

2.which指物，在定语从句中可作主语或宾语。

The bike which is made in Tianjin sells well.天津产的自行车销售很好。(主语)

The fish which we bought were not fresh.我们买的鱼不新鲜。(宾语)

3.who, whom指人，在定语从句中可作主语或宾语。

The boy who broke the window is called Tom.打碎窗户的男孩叫Tom. (主语)

The person to whom he is talking is my father.正在和他谈话的那个人是我父亲。(宾语)

4.whose指人或物，在定语从句中作定语。

The girl whose bag is new is called Ann.新书包的那个女孩叫Ann。(指人)

He lives in a house whose widows open to the south.他住在窗户朝南的那所房子。(指物)

三、只用which不用that的情况：

1.在介词后只用which，不能用that。

This is the bank in which the robbery happened.这是那所发生抢劫案的银行。

2.先行词本身是that时，只能用which，不能用that。

The clock is that which tells the time.钟表是用来报时的。

四、只用that不用which的情况：

1.先行词被形容词最高级修饰时只能用that。

This is the most beautiful mountain that I have seen. 这是我所见过的最美丽的山。

2.先行词被序数词修饰时只能用that。

The first English novel that I read was Thirty-nine Steps.我读的第一本英文小说是《39级台阶》。

3. 先行词前有all, any, no, little, much, many, the only, the very, the last等修饰词时只能用that。

Here are all the books that I have.　这就是我所有的书。

This is the only book that I like.这是我唯一喜欢的一本书。

4.先行词是everything, something, anything, all, none, much, little, many, few等不定代词时，只能用that。

Finally, the thief handed in everything that he had stolen.最后小偷交出了他所偷的东西。

5.先行词同时含有“人”和“物”的名词时，只能用that。

I can remember the people and some pictures that I saw in the room.我能记得我在房间里看到的人和一些图画。

6.先行词是the one时，只能用that。

This is the one that you want.　这就是你想要的。

7.在以who引导的疑问句后，为了避免重复，只能用that。

Who is the girl that is standing there? 站在那边的那个女孩是谁?

五、在介词后只能用whom，不能用who。

The girl to whom I talked just now is from America. 我刚刚与之谈话的那个女孩是来自美国的。