關係代詞whom在口語和非正式語體中常用who代替，可省略。以下內容是小編為您精心整理的定語從句先行詞位置，歡迎參考！
定語從句先行詞位置
當代詞 that 用作先行詞後接定語從句時，定語從句通常用關係代詞which來引導。如：
We have that which we need. 我們需要的東西都有了。
That which I say and do is my own affair. 我說什麼做什麼是我自己的`事。
The true cost often differs from that which had first been projected. 實際成本經常與最初計劃的有所不同。
What is that which you have just stuffed into the plastic cup? 你剛才塞在塑料杯裡的是什麼東西?
They say the only real knowledge is that which can be measured. 據說唯一真實的知識是可以檢驗的知識。
但 that which 這一說法相當正式，在現代英語中通常改用 what。如：
That which (=What) many people say is not always true. 很多人說的話並不表示一定是真的。
順便說一句，that 後可接定語從句，但 this 後習慣上不接定語從句。
定語從句知識點
指人，在從句中做主語
(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，在定語從句中充當賓語，常可省略。
(1) Mr. Liu is the person (whom) you talked about.
注意：關係代詞whom在口語和非正式語體中常用who代替，可省略。
(3) The man who/whom you met just now is my friend.
3. which指物，在定語從句中做主語或者賓語，做賓語時可省略
(1) Football is a game which is liked by most boys. ( which 在句子中做主語)
(2) This is the pen (which) he bought yesterday. ( which 在句子中做賓語)
4. that指人時，相當於who或者whom;指物時，相當於which。
在賓語從句中做主語或者賓語，做賓語時可省略。
(5) The people that/who come to visit the city are all here. (在句子中做主語)
(6) Where is the man that/whom I saw this morning? (在句子中做賓語)
5. whose通常指人，也可指物，在定語從句中做定語
(1) He has a friend whose father is a doctor.
(2) I lived in a house whose roof has fallen in.
whose指物時，常用以下結構來代替
(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?
