定語從句在句中相當於一個形容詞，下面定語從句用法的總結是小編想跟大家分享的，歡迎大家瀏覽。
一.定語從句及相關術語
1.定語從句：修飾某一句中的.名詞或代詞的從句稱爲定語從句，一般緊跟在它所修飾的先行詞後面。被修飾的詞稱爲先行詞。
2.關係詞：引導定語從句的關聯詞稱爲關係詞
關係詞有關係代詞和關係副詞。關係代詞有that, which, who, whom, whose, as等;關係副詞有where, when, why等。
關係詞常有3個作用：1，引導定語從句。2，代替先行詞。3，在定語從句中擔當一個成分。
二.關係代詞引導的定語從句
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 on the bus.
(2) Mr. Ling is just the boy whom I want to see.
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.
(2) This is the pen (which) he bought yesterday.
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 number of the people that/who come to visit the city each year
rises one million.
(6) Where is the man that/whom I saw this morning?
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 once 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.
(4)The classroom the door of which is broken will soon be repaired.
(5)Do you like the book whose cover is yellow? (6)Do you like the book the color of which is yellow?
三.介詞+關係代詞引導的定語從句
1. 關係代詞在定語從句中做介詞賓語時，從句常由介詞+關係代詞引導
(1)The school (that/which) he once studied in is very famous.
(2)The school in which he once studied is very famous.
(3)Tomorrow I will bring here a magazine (that/which) you asked for.
(4)Tomorrow I will bring here a magazine for which you asked.
(5)We’ll go to hear the famous singer (whom/that/who) we have often talk-ed about.
(6) We’ll go to hear the famous singer about whom we have often talked.
2.關係代詞前的介詞的選擇
* 由先行詞的習慣搭配或根據先行詞的需要。
(1) The speed at which light travels is 300,000 km per second. (at the speed of …以…速度)
(2) The reason for which he didn’t come to school was that he was ill. (for a certain reason 由於某種原因)
* 介詞可能是從句短語動詞的一個固定部分或固定搭配
(3) Don’t bring children to see the animals of which they are afraid. (be afraid of 害怕)
(4) This is the teacher from whom I borrowed the book. (borrow from…從…借入
注意：1. 含有介詞的動詞短語一般不拆開使用，如：look for, look after, take care of等
(1) This is the watch which/that I am looking for. (T)
(2) This is the watch for which I am looking. (F)
2. 若介詞放在關係代詞前，關係代詞指人時用whom，不可用who或者that;指物時用 which，不能用that;關係代詞是所有格時用whose
(1) The man with whom you talked is my friend. (T)
(2) The man who/that you talked with is my friend. (F)
(3) The plane in which we flew to Canada is very comfortable. (T)
(4) The plane in that we flew in to Canada is very comfortable. (F)
3. “介詞+關係代詞”前可有some, any, none, both, all, neither, most, each, few等代詞或者數詞
(1) He loved his parents deeply, both of whom are very kind to him.
(2) In the basket there are quite many apples, some of which have gone bad.
(3) There are forty students in our class in all, most of whom are from big cities.
四.關係副詞引導的定語從句
1. when指時間，在定語從句中做時間狀語
(1) I still remember the day when I first came to the school.
(2) The time when we got together finally came.
2. where指地點，在定語從句中做地點狀語
(1) Shanghai is the city where I was born.
(2) The house where I lived ten years ago has been pulled down.
3. why指原因，在定語從句中做原因狀語
(1) Please tell me the reason why you missed the plane.
(2) I don’t know the reason why he looks unhappy today.
注意：1.關係副詞引導的從句可以由“介詞+關係代詞”引導的從句替換
(1) The reason why/ for which he refused the invitation is not clear.
(2) From the year when/in which he was going to school he began to know what he wanted when he grew up.
(3) Great changes have taken place in the city in which./where I was born.
2.當先行詞爲時間、地點、原因名詞時，如果在從句中不是作狀語時，不可用關係副詞引導。
(1)The reason (that/which) he gave for being late is that his mother was ill.
(2)They make me think of the happy days (that/which) we spent together.
(3)Is this factory the one (that/which) they visited the day before yester- day.
