一： 先行詞： 被定語從句所修飾的詞
二： 關系代詞：用來連接定語從句，并在從句中代表先行詞的代詞。
先行詞是物： which that
先行詞是人： who that
在從句中的作用： 主語、賓語、表語
e.g. They had a radio. / It could send out messages.
They had a radio which/ that could send out message. (主語)
The girl is my best friend. / She spoke just now.
The girl who/ that spoke just now is my best friend. （主語）
He always buys some books. / He never read them.
He always buys some books (which/ that) he never read. (賓語)
注意點：
1.） 定語從句一般直接跟在先行詞的后面：
e.g. The man who lives next door sells vegetables.
The man sells vegetables who lives next door. ( × )
The car which my uncle just bought was destroyed in the earthquake.
The car was destroyed in the earthquake which my uncle just bought. ( × )
2．）關系代詞在從句中作賓語時可以省略：
e.g. The young man ( who ) you saw was our manager.
There is something ( that ) we must keep in mind.
3.) 關系代詞在從句中作介詞的賓語時，介詞常可以提前，但介詞提前時， 關系代詞只能用which 或 whom
e.g. The man is a famous runner. / You talked to him just now.
The man to whom you talk just now is a famous runner.
The chair is made of wood. / He is sitting on it now.
The chair on which he is sitting now is made of wood.
He is a library assistant. / I borrowed some books from him.
He is a library assistant from whom I borrowed some books.
It is a famous school. / He graduated from it 3 years ago.
It is a famous school from which he graduated 3 years ago.
The service should be improved. / The students complain a lot about it.
The service about which the students complain a lot should be improved.
有一些動詞短語中的介詞是固定搭配，不可以拆開，一般還是放在動語之后，不提前：
e.g. He is the student. / The teachers are looking for him.
He is the student who the teachers are looking for.
The number of the children is 30. / She takes care of the children.
The number of the children who she takes care of is 30.
三： whose 的用法：
關系代詞與其后的名詞構成所有格，即“的”時，它既可以修飾指人的先行詞，也可以修飾指物的先行詞。
e.g. The girl is my daughter. / Her work got the first prize.
The girl whose work got the first prize is my daughter.
Do you know anyone? / His family is in Xi’an.
The book is not mine. / The cover of it is red.
I live in the room. / The windows of it face south.
The chair has been repaired. / The leg of it was broken.
四：限制性定語從句和非限制性定語從句：
限制性定語從句：主句和從句不隔開，從句不能省略，否則就會失掉意義不能成立。
He is reading a book which is too difficult for him.
Here is the boy who damaged the glass.
非限制性定語從句：主句和從句用逗號隔開，從句對修飾的部分起到進一步說明的作用，拿掉后其它部分的語意仍保持完整。
e.g. The book is written by Guo Jinming, who is only 19 years old.
Bob’s father, who was an engineer, spent 4 years in Egypt.
Shanghai, which is developing fast, has become one of world’s trade center.
注意點：
非限制性定語從句不能用that引導.
e.g. She is very fond of French, which indeed she speaks quite well.
which還可以用來指代上文中的一件事情.
e.g. Their house is washed away by the floods, which made them very sad.
He lost his job finally, which was exactly what we wanted.
介詞＋which:
The picture ______ he paid $100 was once owned by a king.
Can you think of a situation ________ this word can be used?
I’m grateful to him for that advice, ______ I owed all my success.
關系副詞： when where why
當先行詞是表示時間的名詞，用when，在定語從句中充當時間狀語，這時一般可以用介詞＋which來代替:
e.g. I will never forget the day./ I went to university on that day.
I will never forget the day when/ on which I went to university.
He still remember the morning. / The earthquake happened on that morning.
He still remember the morning when/ on which the earthquake happened.
當先行詞是表示地點的名詞，用where，在定語從句中充當地點狀語，這時一般可以用介詞＋which來代替:
e.g. This is the house. / He used to live in the house.
This is the house where/ in which he used to live.
I know of a place. / We can swim in that place.
I know of a place where/ in which we can swim.
Is there any shop around? / I can buy a pen in the shop.
Is there any shop around where/ in which I can buy a pen.
先行詞是表示原因的名詞，即reason，用why，在定語從句中充當原因狀語，這時一般可以用for ＋which來代替:
e.g. I don’t know the reason. / He did it for this reason.
I don’t know the reason why/ for which he did it.
The reason was not clear. / He was fired for it.
The reason why/ for which he was fired was not clear.
注意點：
當表示時間、地點和原因的名詞在從句中不是作狀語，而是在從句中作主語或賓語時，還是應用which/ that
e.g. This is the date _______ we’re proud of.
This is the date _______ he was born.
I will never forget the time ______ we spent together.
This is the factory _______ my mother works.
This is the factory _______ we visited last week.
Is this factory you visit last week?
A. the one B. where C. which D. that
This factory is the one (that/ which) you visit last week.
I don’t believe the reason _____ he gave for his decision.
Another reason _______ he made this decision is that he had to consider the feelings of others.
關系詞的選擇
Ａ．只用that
a.當先行詞是不定代詞，如all, everything, anything, nothing, much, few, little, none, the one等
All that can be done has been done.
I didn’t mean this one; I mean the one that was bought yesterday.
b.先行詞（指物的）前面有only, few, one of, little, no, all, every, very等詞修飾時
There’s no difficulty that we can’t overcome.
I’ve read all the books that can be borrowed here.
c.先行詞被序數詞first, last, next等或形容詞的最高級修飾時
This is the first letter that I’ve written in Japanese.
She is the most careful girl that I’ve ever known.
d.當先行詞既有人又有物時
They talked about the teachers and schools that they had visited.
The speaker talked of some writers and books that were unknown to us.
e.當先行詞是系動詞be后面的表語或關系詞本身是從句的表語時
China isn’t the country that she used to be 50 years ago.
He is no longer the man that he used to be.
It’s a book that will help you a great deal.
f．當主句是以who, which或what開頭的特殊疑問句時
Who is the man that is waiting at the bus stop?
Which is the car that overtook us yesterday?
g. 當主句以There be…結構開頭時，或關系代詞在there be…結構中作實義主語，先行項為物
There is a seat in the corner that is still free.
There are two tickets of the film that are for you.
The 9.15 is the fastest train that there has ever been.
h. 當先行詞是what時
What did you hear that made you so angry?
i.當先行詞是基數詞時
Yesterday I caught two fish and put them in a basin of water. Now you can see the two that are still alive.
B. 只用which
a. 在非限制性定語從句，充當主語或定語
They have three houses, which are built of stone.
b. 當關系代詞前有介詞時
This is the factory in which we once worked.
We study in the classroom of which the doors face south.
c．當先行詞本身that是時
What’s that which flashed in the sky just now?
d. 當關系代詞后面帶有插入語時
Here is the English grammar book which, as I have told you, will help improve your English.
I’ve bought you some books which I think may interest you.
C.只用who不用that
a.先行詞是one, ones或anyone時
One who does not work hard will never succeed.
Anyone who breaks the law should be punished.
She is the only one of the students who has been to the USA.
b.先行詞為those 或被those修飾，指人時
Those who learn not only from books but also through practice will succeed.
c.在以there be…的句子中，先行詞為人時
There is a comrade outside who wants to see you.
d. 當定語從句中又有定語從句，且先行項都為人時
The student that won the first prize is the monitor who works hard.
e.當指人的先行項被一些指物的名詞修飾時
There ‘s only one student in the school who I want to see.
Do you know the woman in blue with a baby on her back who is working in the fields?
f. 在非限制性定語從句中指人
I met a friend of mine in the street, who had just come from America.
g.定語從句中有插入語時, 并不影響關系代詞和副詞的選擇。
Jackson is a man who I believe is honest.
He won another award, which I think is the result of his hard work.
D.在定語從句中，whose作定語， 其先行項既可以是人，又可以是物
Lei Feng was a great communist fighter whose death was weightier than Mount Tai.
Where’s the window whose glass is broken?
E. 在定語從句，關系副詞when, where, why與關系代詞which, that的關系
July 1st, 1921 is the day that/which we Chinese should always remember.
This is the place that/which they visited last year.
Please give me a reason that/which could account for your absence.
I still remember the day when(=on which) I joined the army.
This is the room where(=in which) Luxun once lived.
Another reason why(=for which) he works hard is that he has pass the exam.
F. as, which的比較
a.在非限制性定語從句中，均可替代整個主句或句中某個部分，在從句中作主語，賓語，表語．如從句在主句之后，兩者皆可用
They failed in the exam, as/which is natural.
She seems a scientist, as/which in fact she is.
Grammar is not a set of dead rules, which/as I have said before.
b.如從句在主句之前，用as
As we all know, his parents were killed in this war.
As is known to all, the earth travels around the sun.
c.如關系代詞代表主句全句意思，有＂正如．．．＂＂就象．．．＂之意時，用as
We won the match, as we had expected.
He agreed to the plan, as was to be expected.
d. 當先行項被the same, such, so修飾時，用as
This is the same book as you bought yesterday.同類書 (比較：This is the same book that you bought yesterday.同一本書)
Don’t believe in such men as praise you to your face.
I never give my students so difficult a question as no one can work out.
e. 當從句內容對主句內容起消極作用，則用which
The young man cheated his friend out of much money, which was disgra 定語從句小結
. as 也可以用來引導非限制性定語從句， 用來指待一件事，這時它的位置可以放在句首、句中和句尾。
e.g. He is an American, as/which we know from his accent.
As we know from his accent, he is an American.
He, as we know from his accent, is an American.
As has been said above, grammar is not a set of dead rules.
Grammar, as has been said above, is not a set of rules.
Grammar is not a set of dead rules, as/which has been said above.
正如: As everyone knows, as you may still remember, as you said, as I can see, as has been mentioned above, as you may have heard, and etc.
定語從句的練習：
I passed him a glass of whiskey, ______ he drank at once.
He spoke to me in a way _______ I don’t at all like.
It is a famous university ________ he graduated 3 years ago.
Are you the lady ______ asked for help?
The service __________ students complain a lot should be improved.
He works in a college ______ students are all women.
The picture ______ he paid $100 was once owned by a king.
Can you think of a situation ________ this word can be used?
We can see very clearly the method ______ the computers work.
_______ he introduced just now, Dr. Baker is an expert in Biology.
I’m grateful to him for that advice, ______ I owed all my success.
This is the famous star ______ photos are on this magazine.
The science of medicine, ________ progress has been very rapid lately, is perhaps the most important of all the science.