3.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.

(2) This is the pen (which) he bought yesterday.

如果在从句中做宾语,就用whom或who.比如: He is the man whom/who I talk to.

如果是在从句中作主语就只能用who.比如: He is the man who has an English book.

2. 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 on the bus.

(2) Mr. Ling is just the boy whom I want to see.

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.

1.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.

1.定语从句：修饰一个名词或代词的从句称为定语从句，一般紧跟在它所修饰的先行词后面。2.关系词：引导定语从句的关联词成为关系词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where, when, why等。关系词常有3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。

(三)关系代词引导的定语从句

8. 当从句的逻辑主语是some, any, no, somebody, anybody, nobody, something, anything, everything或nothing时，常用there is来引导。

(二)定语从句及相关术语

7. whose是关系代词，修饰名词作定语，相当于所修饰成分的前置所有格。

6. when引导定语从句表示时间［注］值得一提的是，表示时间“time"一词的定语从句只用when引导，有时不用任何关系代词，当然也不用that引导 。

By the time you arrive in London, we will have stayed there for two weeks. I still remember the first time I met her. Each time he goes to business trip, he brings a lot of living necessities, such as towers, soap, toothbrush etc.

5. where是关系副词，用来表示地点的定语从句 。

4. who和whom引导的从句用来修饰人，分别作从句中的主语和宾语，whom作宾语时，要注意它可以作动词的宾语也可以作介词的宾语 。

3. 代表物时多用which，但在带有下列词的句子中用that而不用which，这些词包括all, anything, much等，这时的that常被省略 。