1、that指人时，相当于who或者whom;指物时，相当于which。 在宾语从句中做主语或者宾语，做宾语时可省略。 (5) The people that/who come to visit the city are all here. (在句子中做主语) (6) Where is the man that/whom I saw this morning? (在句子中做宾语)
2、which指物，在定语从句中做主语或者宾语，做宾语时可省略 (1) Football is a game which is liked by most boys. ( which 在句子中做主语) (2) This is the pen (which) he bought yesterday. ( which 在句子中做宾语)
3、whom指人，在定语从句中充当宾语，常可省略。 (1) Mr. Liu is the person (whom) you talked about. 注意：关系代词whom在口语和非正式语体中常用who代替，可省略。 (3) The man who/whom you met just now is my friend.
4、whose通常指人，也可指物，在定语从句中做定语 (1) He has a friend whose father is a doctor. (2) I lived in a house whose roof has fallen in. whose指物时，常用以下结构来代替 (3)The classroom whose door is broken will soon be repaired. =The classroom the door of which is broken will soon be repaired. (5)Do you like the book whose color is yellow? =Do you like the book the color of which is yellow?
5、who指人，在从句中做主语 (1)The boys who are playing football are from Class One. (2)Yesterday I helped an old man who lost his way.
6、定语从句关系代词句子 关系词通常有下列三个作用：1)引导定语从句;2)代替先行词;3)在定语从句中担当一个成分。 关系代词有that，which，who，whom，whose，as等; 一：关系代词的用法 关系代词 指代对象及在从句中所作的成分 使用要点 that 即指人又指物;作主语或宾语(作宾语时可省略) 只用于限制性定语从句中，介词后面不能跟that。 当代替物时，可以与which通用。 Yesterday Emily was wearing the new dress that I gave her. 昨天艾米丽穿了我送给她的新衣服。 I have a friend that likes listening to classical music我有个朋友喜欢听古典音乐。 which 指物;作主语或宾语(作宾语时可省略) 在非限定性定语从句中，只宜用which,不能用that.在限定性定语从句中，可用在介词之后。 My parents live in a house which is more than 100 years old 我的`父母住在一座具有100多年历史的房子里 who,whom 指人;作主语或宾语(whom常可省略) 先行词必须为人。Who可代替在从句中担任宾语的whom,若前有介词，须用whom A couch potato is a person who spends a lot of time watching TV. “A couch potato”指那种成天沉湎于电视中的人。 The student(whom)I taught two years ago has joined the army. 我两年前教的那个学生已经参军了。 whose 既指人又指物;作定语 是代词的所有格， 代物时，相当于of which。 The room whose window faces south is mine. 那个窗户朝南的房间是我的。 注意：whose指物时，常用of which结构来代替。如： The classroom whose door is broken will soon be repaired. =The classroom the door of which is broken will soon be repaired.
