2. 只能用which，不用that 的情况：

(1) 非限制性定语从中。The meeting was put off, which was exactly what we wanted.

(2) 定语从句由介词+关系代词引导，先行词是物时。例如：

　　　 The thing about which he is talking is of great importance.

六，关系词的省略：

(1)　 关系代词在从句中作宾语时： He is the man(who/whom/that) I talked to yesterday.

(2)　 关系代词that在分句中作补语时：He has changed. He is not the man(that) he was.

(3)　 当关系代词作主语，只有主句是由it is, that is ,there is 引导时才能省略：

That was his mother just went away.

(4)　 在the time when; the place where; the reason why 结构中，非正式语体可以省略;

I’ll never forget the day (when) we first met.

The reason (why) he was late again is unknown. That’s the place I stayed last night.

1. 只能使用that,不用which 的情况：

(1) 先行词是all, few, little, nothing, everything, anything 等不定代词时。例如：

　　　　 All that he said is true.　

(2) 先行词被only, no, any, all,等词修饰时。例如：

　　　　 He is the only foreigner that has been to that place.　

(3) 先行词是序数词或被序数词修饰的词。例如：

He was the second (person) that told me the secret.

(4) 先行词是形容词最高级或被形容词最高级修饰的词。

This is the best book (that) I have read this year.

(5) 先行词既包括人又包括物时。例如：

　He talked about the people and the things he remembered.

(6)主句以who, what，which 开头的特殊疑问句

Who is the girl that is wearing a red coat?

That was the room in which we had lived for ten years. = That was the room　

which we had lived in for ten years.

7. where 指地点，在从句中作状语。例如：This is the house where we lived last year.

6. when 指时间，在定语从句中作状语。例如：

　　 I’ll never forget the time when we worked on the farm.

5. that多指物，有时也指人，在定语从句中作主语或宾语。例如：

I’ve read the newspaper that(which) carries the important news.

Who is the person that is reading the newspaper over there?

4. which指物，在定语从中作主语或宾语。例如：

A dictionary is a book which gives the meaning of words.

Here is the book (which) the teacher mentioned yesterday.

3. whose 指人，在定语从句中作定语。例如：

The girl whose mother is ill is staying at home today.

I know the boy whose father is a professor.

2. whom指人，在定语从句中作宾语。例如：

Do you know the young man (whom) we met at the gate？

Mr. Lee (whom) you want to see has come.

1. who 指人，在定语从句中作主语。例如：

The person who broke the window must pay for it.

The boy who is wearing the black jacket is very clever.