定语从句先行词位置
定语从句先行词位置
当代词 that 用作先行词后接定语从句时，定语从句通常用关系代词which来引导。如：
We have that which we need. 我们需要的东西都有了。
That which I say and do is my own affair. 我说什么做什么是我自己的'事。
The true cost often differs from that which had first been projected. 实际成本经常与最初计划的有所不同。
What is that which you have just stuffed into the plastic cup? 你刚才塞在塑料杯里的是什么东西?
They say the only real knowledge is that which can be measured. 据说唯一真实的知识是可以检验的知识。
但 that which 这一说法相当正式，在现代英语中通常改用 what。如：
That which (=What) many people say is not always true. 很多人说的话并不表示一定是真的。
顺便说一句，that 后可接定语从句，但 this 后习惯上不接定语从句。
定语从句知识点
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.
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.
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.
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. ( 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)
4. 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)
5. 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?
