关系词有关系代词和关系副词。关系代词有that, which, who, whom, whose, as等；关系副词有when, where, why等。
The man who is shaking hands with my father is a policeman. 该句中,who is shaking hands with my father 是定语从句,修饰先行词the man, “who”是引导定语从句的关系词,代替先行词the man,在定语从句中作主语。
The boys who are playing football are from Class One. 正在踢足球的男孩是一班的。
Those who want to go to the museum must be at the school gate at 7 tomorrow morning. 想去博物馆的人必须在明晨7点到大门口集合。
Yesterday I helped an old man who had lost his way. 昨天我帮助了一位迷路的老人。
That is the teacher who teaches us physics. 那就是教我们物理的老师。
Mr Liu is the person （whom） you talked about on the bus. 刘先生就是你们在公共汽车上谈论的那个人。
Li Ming is just the boy （whom） I want to see. 李明正是我想要见的男孩。
The professor （whom） you are waiting for has come. 你正在等的教授已经来了。
The girl （whom） the teacher often praises is our monitor. 老师经常表扬的那个女孩是我们的班长。
注意：关系代词whom 在口语或非正式文体中常可用who 来代替,也可省略。
The man （whom / who）you met just now is my old friend.
Football is a game which is liked by most boys. 足球是大多数男孩所喜欢的运动。
The factory which makes computers is far away from here. 制造计算机的那家公司离这儿很远。
He likes to read books which are written by foreign writers. 他喜欢外国作家写的书。
The house which is by the lake looks nice. 湖边的那幢房子看上去很漂亮。
This is the pen （which） he bought yesterday. 这是他昨天买的钢笔。
The film （which） they went to see last night was not interesting at all. 他们昨晚看的电影一点意思也没有。
4.That 指人时,相当于who 或whom；指物时,相当于which.。在定语从句中作主语或宾语,作宾语时常可省略。
The number of people that / who come to visit this city each year reaches one million. 每年来参观这座城市的人数达一百万。
Where is the man that / whom I saw this morning？ 我今天早上看到的那个人在哪儿？
The person that /whom you introduced to me is very kind. 你介绍给我的那个人很友好。
The season that / which comes after spring is summer. 春天以后的季节是夏季。
Yesterday I received a letter that / which came from Australia. 昨天我收到了一封来自澳大利亚的信。
I visited a scientist whose name is known all over the country. 我拜访了一个全国知名的科学家。
He has a friend whose father is a doctor. 他有一个爸爸当医生的朋友。
I once lived in the house whose roof has fallen in. 我曾经住在那幢屋顶已经倒塌了的房子里。
The classroom whose door is broken will soon be repaired.
The classroom the door of which is broken will soon be repaired.
Do you like the book whose cover is yellow？
Do you like the book the cover of which is yellow？
The school （which / that） he once studied in is very famous.
The school in which he once studied is very famous. 他曾经就读过的学校很出名。
Tomorrow I'll bring here the magazine （which / that） you asked for.
Tomorrow I'll bring here the magazine for which you asked.明天我将把你要的杂志带来。
This is the boy （whom / who / that） I played tennis with yesterday.
This is the boy with whom I played tennis with yesterday. 这是我昨天跟他打台球的男孩。
We'll go to hear the famous singer （whom / who / that） we have often talked about.
We'll go to hear the famous singer about whom we have often talked.我们将去听那位我们经常谈论的著名歌唱家演唱。
The manager whose company I work in pays much attention to improving our working conditions.
The manager in whose company I work pays much attention to improving our working conditions.
注意：1. 含有介词的短语动词一般不拆开,介词仍放在短语动词的后面。如：look for, look after, take care of 等。
This is the watch （which / that） I am looking for. （正） 这是我正在找的手表。
This is the watch for which I am looking . （误）
The babies （whom / who / that） the nurse is looking after are very healthy. （正） 那个保姆照看的小宝宝们都很健康。
The babies after whom the nurse is looking are very healthy. （误）
The man with whom you talked just now is my neighbour. （正） 你刚才跟他谈话的那个人是我的邻居。
The man with that / who you talked just now is my neighbour. （误）
The plane in which we flew to Canada was really comfortable. （正）我们去加拿大所乘坐的飞机实在很舒服。
The plane in that we flew to Canada was really comfortable. （误）
3.“介词+关系代词”前还可有some, any, none, all, both, neither, many, most, each, few等代词或者数词。如：
He loves his parents deeply, both of whom are very kind to him. 他深深地爱着他的父母,他们俩待他都很好。
In the basket there are quite many apples, some of which have gone bad. 篮子里有好些苹果,有些已经坏了。
There are forty students in our class in all, most of whom are from big cities. 我们班总共有40个学生,大多数来自大城市。
Up to now, he has written ten stories, three of which are about country life. 迄今为止,他写了10部小说,其中3部是关于农村生活的。