一： 先行词： 被定语从句所修饰的词
二： 关系代词：用来连接定语从句，并在从句中代表先行词的代词。
先行词是物： which that
先行词是人： who that
在从句中的作用： 主语、宾语、表语
e.g. They had a radio. / It could send out messages.
They had a radio which/ that could send out message. (主语)
The girl is my best friend. / She spoke just now.
The girl who/ that spoke just now is my best friend. （主语）
He always buys some books. / He never read them.
He always buys some books (which/ that) he never read. (宾语)
注意点：
1.） 定语从句一般直接跟在先行词的后面：
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．）关系代词在从句中作宾语时可以省略：
e.g. The young man ( who ) you saw was our manager.
There is something ( that ) we must keep in mind.
3.) 关系代词在从句中作介词的宾语时，介词常可以提前，但介词提前时， 关系代词只能用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.
有一些动词短语中的介词是固定搭配，不可以拆开，一般还是放在动语之后，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：
关系代词与其后的名词构成所有格，即“的”时，它既可以修饰指人的先行词，也可以修饰指物的先行词。
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：限制性定语从句和非限制性定语从句：
限制性定语从句：主句和从句不隔开，从句不能省略，否则就会失掉意义不能成立。
He is reading a book which is too difficult for him.
Here is the boy who damaged the glass.
非限制性定语从句：主句和从句用逗号隔开，从句对修饰的部分起到进一步说明的作用，拿掉后其它部分的语意仍保持完整。
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.
注意点：
非限制性定语从句不能用that引导.
e.g. She is very fond of French, which indeed she speaks quite well.
which还可以用来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.
介词＋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.
关系副词： when where why
当先行词是表示时间的名词，用when，在定语从句中充当时间状语，这时一般可以用介词＋which来代替:
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.
当先行词是表示地点的名词，用where，在定语从句中充当地点状语，这时一般可以用介词＋which来代替:
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.
先行词是表示原因的名词，即reason，用why，在定语从句中充当原因状语，这时一般可以用for ＋which来代替:
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.
注意点：
当表示时间、地点和原因的名词在从句中不是作状语，而是在从句中作主语或宾语时，还是应用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.
关系词的选择
Ａ．只用that
a.当先行词是不定代词，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.先行词（指物的）前面有only, few, one of, little, no, all, every, very等词修饰时
There’s no difficulty that we can’t overcome.
I’ve read all the books that can be borrowed here.
c.先行词被序数词first, last, next等或形容词的最高级修饰时
This is the first letter that I’ve written in Japanese.
She is the most careful girl that I’ve ever known.
d.当先行词既有人又有物时
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.当先行词是系动词be后面的表语或关系词本身是从句的表语时
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．当主句是以who, which或what开头的特殊疑问句时
Who is the man that is waiting at the bus stop?
Which is the car that overtook us yesterday?
g. 当主句以There be…结构开头时，或关系代词在there be…结构中作实义主语，先行项为物
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. 当先行词是what时
What did you hear that made you so angry?
i.当先行词是基数词时
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. 在非限制性定语从句，充当主语或定语
They have three houses, which are built of stone.
b. 当关系代词前有介词时
This is the factory in which we once worked.
We study in the classroom of which the doors face south.
c．当先行词本身that是时
What’s that which flashed in the sky just now?
d. 当关系代词后面带有插入语时
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.先行词是one, ones或anyone时
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.先行词为those 或被those修饰，指人时
Those who learn not only from books but also through practice will succeed.
c.在以there be…的句子中，先行词为人时
There is a comrade outside who wants to see you.
d. 当定语从句中又有定语从句，且先行项都为人时
The student that won the first prize is the monitor who works hard.
e.当指人的先行项被一些指物的名词修饰时
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. 在非限制性定语从句中指人
I met a friend of mine in the street, who had just come from America.
g.定语从句中有插入语时, 并不影响关系代词和副词的选择。
Jackson is a man who I believe is honest.
He won another award, which I think is the result of his hard work.
D.在定语从句中，whose作定语， 其先行项既可以是人，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. 在定语从句，关系副词when, where, why与关系代词which, that的关系
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的比较
a.在非限制性定语从句中，均可替代整个主句或句中某个部分，在从句中作主语，宾语，表语．如从句在主句之后，两者皆可用
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.如从句在主句之前，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.如关系代词代表主句全句意思，有＂正如．．．＂＂就象．．．＂之意时，用as
We won the match, as we had expected.
He agreed to the plan, as was to be expected.
d. 当先行项被the same, such, so修饰时，用as
This is the same book as you bought yesterday.同类书 (比较：This is the same book that you bought yesterday.同一本书)
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. 当从句内容对主句内容起消极作用，则用which
The young man cheated his friend out of much money, which was disgra 定语从句小结
. as 也可以用来引导非限制性定语从句， 用来指待一件事，这时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.
定语从句的练习：
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.