1、关系代词who

(1) 、关系代词who在句中做主语, 它的先行词是指人的名词或代词

She looked at Jeff  who was waving his arms.她看着正在招手的杰夫。

I have a friend who likes listening to classical music.我有个喜欢古典音乐的朋友.

（2）、关系代词who可以引导非限定性定语从句

Betty , who has never been abroad, is studying English very well.

He , who led the United States through these years, was shot on April 14, 1965.

（3）、先行词如果是指人物成员的集体名词，关系代词也用who

The family who live upstairs are fond of music.住在楼上的这家人喜欢音乐.

This class, who have got tickets will go to the theatre this morning.这个班级的同学都拿到了票,今天上午去看戏.

2、关系代词whom

（1）、关系代词whom在从句中做宾语，口语中常省去，它的先行词也是指人的名词或代词

The family (whom )I ’m staying with lives in town.

Where is the comrade (whom) I saw this morning ?

The boy( whom )John spoke to is my brother.

（2）、定语从句中的介词前置到whom之前 ，whom不可以省略。

The family with whom I ’m staying lives in town.

The boy to whom John spoke  is my brother.

（3）、whom关系代词可以引导非限定性定语从句

His mother , whom he loved dearly , died in 1918.

3、关系代词who 和whom 的区别

（1）、在非正式文体中关系代词who可以代替whom做宾语，且可以省略

The family (whom /who)I ’m staying with lives in town.

Where is the comrade (whom/who) I saw this morning  ?

The boy( whom/who )John spoke to is my brother.

（2）、但是如果关系代词在定语从句中做介词的宾语，且这个介词前置到关系代词之前的位置时，whom不能被who代替，而且也不可以省略。

The family with whom I ’m staying lives in town.

The boy to whom John spoke is my brother.

（3）、在非限定性定语从句中必须使用whom ，不可以用who代替whom充当宾语而且不可以省略。

His mother ,  whom he loved dearly , died in 1918.

XiaoHua ,  whom you met with in the street last month, went abroad two days ago.

4、关系代词that

关系代词that在句中可以做主语、宾语、表语，做宾语时，可以省略不用。它的先行词可以是人的名词或代词，也可以是指事物的名词或者是代词。但是它不可以引导非限制性定语从句。

The earthquake that hit the city in 1906 was the biggest in American history.

                                                                   (主语)

We don’t know the number of people that lost their homes in the earthquake.

                                                                    (主语)

Luckily none of the people (that) I know were killed in the earthquake.

                                                                     (宾语)

This is the town that I told you about on the plane.                 (宾语)

He is not the man that he used to be.                                (表语)