定語從句（形容詞性從句）
在句中修飾名詞或代詞的從句，因其修飾作用相當于形容詞，故稱形容詞性從句，即通常所說的定語從句。被定語從句修飾的詞叫先行詞。引導定語從句的有：
1）關系代詞： 先行詞為人：who, whom, that, whose
先行詞為物：which, that, whose
2）關系副詞：when, where, why
注意： 關系詞起三個作用：①連接先行詞和定于從句②替代先行詞③在從句中擔任成分
what不能引導定語從句。定語從句一般緊跟在先行詞后，但有時也被一個短語隔開。
例如：I was the only person in my office who was invited.
1. 關系代詞和關系副詞的一般用法
1) 關系代詞在從句中充當主語、賓語或表語等成分，關系代詞充當賓語、表語時可以省略：
Here’s a fellow who just walks into a bank and helps himself to so much money. （作主語）
He is no longer the man (that) he used to be. （作表語）
This is the book（that/which）I referred to in my talk. (作賓語)
whose在定語從句中置于名詞之前，充當定語，既可指人，又可指物。
whose +n.= the +n.+ of which/whom。例如：
Please pass me the dictionary whose cover is black. （指物）
=Please pass me the dictionary the cover of which is black.
The doctor, whose name was Johnson, lived in a small town in the north of England. （指人）
=The doctor, the name of whom was Johnson, lived in a small town in the north of England.
2) 關系副詞when, where, why在從句中充當狀語，分別可表時間、地點或原因。
I will never forget the day when I first came to Beijing.
This is the house where Lu Xun once lived.
I know the reason why he came late.
注：先行詞是the way時，其后的定語從句關系詞有三種，例如：
I like the way in which / (that)the teacher gives his lessons.
從句缺少的是主語、賓語還是狀語是確定用關系代詞還是關系副詞的關鍵。也就是說要看先行詞在定語從句中擔任什么成分
試比較：
I will never forget the day (which/that) I spent in Hongkong.
( spent是及物動詞，后缺賓語，因此用關系代詞或省略 )
I will never forget the day when/on which Hongkong returned to its motherland.
（ 從句主謂賓結構完整，缺狀語，因此用關系副詞或介詞加關系代詞 ）
The reason （that/which）he gave for not coming to school yesterday is unbelievable.
( gave是及物動詞，后缺賓語，因此用關系代詞或省略 )
The reason why he didn’t come to school yesterday is unbelievable.
（ 從句主謂賓結構完整，缺狀語，因此用關系副詞或介詞加關系代詞 ）
2．限制性定語從句與非限制性定語從句
限制性定語從句對先行詞起限定作用，去掉后主句意義就變得不明確，它與主句之間沒有逗號分隔。例如：
This is a shop that sells personal computers.
The watch that I bought yesterday works well.
非限制性定語從句與主句之間的關系相對松散一些，它對先行詞起補充說明作用，去掉后不影響主句意義。因此，一些具有區別意義的專有名詞及一些表示“唯一”概念的人或物后面常用此類從句。這類從句與主句之間有逗號隔開。例如：
We are all proud of the Great Wall, which is one of the man-made wonders of the world.
My father, who is a doctor, often encourages me to work hard.
注意：在非限制性定語從句中作賓語的關系代詞不能省去。
一種特殊的非限制性定語從句
在非限制性定語從句中，有時根據句子意思，常把some, any, none, all, both, several, many, most, neither, either等詞、分數或百分比與of whom或of which連用。
He has five children, two of whom are abroad.
(比較：He has five children, and two of them are abroad.)
We have tested three hundred types of boots, none of which is/are completely waterproof.
(比較：We have tested three hundred types of boots, but none of them is/are completely waterproof.)
3．介詞+關系代詞的用法
關系代詞緊跟在介詞后面時，不能用that，也不能省略，常用which或whom。
介詞的選用可根據從句中的相關詞組確定，該介詞通�？梢苑旁陉P系代詞之前，也可放在從句之尾。例如：
The man (who/whom/that) I talked about at the meeting is from Beijing University.
=The man about whom I talked at the meeting is from Beijing University.
The palace (which/that) I often pay a visit to was built in the 17th century.
=The palace to which I often pay a visit was built in the 17th century.
但遇固定詞組時，介詞一般緊跟詞組主體，不作前置。如：
Is this the book (which/that) you are looking for? ( 這里介詞for一般不提前，因為look for是固定詞組，意為“尋找”，介詞for若被提前，單個的look意為“看”，句意不符。)
介詞也可結合句意、根據先行詞確定，此時介詞以前置為佳。
Last night I had a dream in which I became a Nobel Prize winner.
The girl with whom I went to the concert yesterday is my sister.
I need a pen with which I can write a letter.
I need a piece of paper on which I can write a letter.
4．關系代詞的一些特定用法：that與which；that與who
1）指物時，關系代詞that和which一般情況下可換用，但以下幾種情況下一般用that，不用which：
①先行詞是all, everything, something, anything, nothing, none, few, little, much等不定代詞；或是先行詞被all, every, some, any, no, few, little等修飾時：
Is there anything (that) I can do for you in town?
I have read all the books (that) you gave me.
注：當something確指某物或某事時，用that或which都可以，如：
There is something that/which keeps worrying me. “有一件事一直令我不安�！�
②先行詞被形容詞最高級或有序數詞the first, the second…, the last修飾時：
This is the best film (that) I have ever seen.
The first place (that) we’ll visit is the Great Wall.
③先行詞被the only，the very修飾時：
The only thing that matters is to find our way home.
This is the very book (that) I’ve been looking for.
④先行詞既有人又有物時：
They talked about the persons and things (that) they remembered in the school.
⑤當主句是由who或which引導的特殊問句時，為避免重復，定語從句中常用that：
Who is the man that is standing by the door?
Who that has common sense will do such a thing?
Which is the dictionary (that) you bought yesterday?
Which that you bought just now is for me?
⑥兩個定語從句，一個用which一個用that
Edison built up a factory which produced things that had never been seen before.
2)用which不用that：
①介詞后②非限制性定于從句中③兩個定語從句，一個用that一個用which
3)當先行詞是anyone, those, he, she等代詞表“人”時，一般用who而不用that：
Anyone who wants a ticket please sign your name here.
Those who want to go to the English party must be at the school gate by 7:30 p.m.
He who doesn’t reach the Great Wall is not a true man.
但當關系代詞在定語從句中作表語時，通常用that而不用who：
He is no longer the man that he used to be.
5．定語從句中的as及其與which的異同
1）as引導的限制性定語從句：
當先行詞有the same, such, as, so修飾時，要用as代替who(m), which, that來引導定語從句：
I’d like to have the same books as are used in your school.
He is not such a person as I expected.
He will marry as pretty a girl as he can find.
注意區別：
It was such a good film that I saw it yesterday.
Don’t talk about such things as you don’t understand.
Here is so big a stone that no one can move it.
Here is so big a stone as no one can move.
His speech was so clear that we could understand well.
He knows as many people as are present.
Yesterday she bought the same book as I have.
He is the same man that gave us a talk last year.
2）as引導的非限制性定語從句與which引導的非限制性定語從句的異同
which和as都可以指代主句中的一部分或整個句子的內容，有時可以互換：
Our team lost the game, as/which was reported in the newspaper.
She was terrified, as/which I could see from her eyes.
區別：①as引導的非限制性定語從句可以放在主句前面、插在主句中間或放在主句末尾；而which引導的非限制性定語從句只能放在主句后面。例如：
As anybody can see, the elephant is like a snake.
=The elephant, as anybody can see, is like a snake.
=The elephant is like a snake, as anybody can see.
Mary was late again, which made the teacher angry.
②as引導的從句有“正如”、“正像”之意，常用句型有：
as we all know, as is known to all, as everybody can see, as is expected等。
例如：As we all know, paper was first made in China.
Which引導的從句是對主句的評論或主句造成的結果。Which= and this
He failed in the experiment, which was unexpected.
He stole the money, which was disgraceful.
6. He is one of the workers who live in the factory.
He is the only one of the workers who has been there.
典型例題分析
1．All ____ is needed is a supply of oil. ( ’89 )
A. the thing B. that C. what D. which
解析：本題考查引導定語從句的關系詞，what只能用于名詞性從句，因此A/D可以排除，又因先行詞為不定代詞all，所以答案為B。
2．He paid the boys $10 for washing ten windows, most of ____ hadn’t been cleaned for at least a year. ( ’90 )
A. these B. those C. that D. which
解析：本題考察非限制性定語從句。從句子結構上看，兩句之間用的是逗號，無連詞連接，故確定為從屬句，介詞后面的關系代詞代物，只能用which，答案為D。
3．In the dark street, there wasn’t a single person ____ she could turn for help. ( ’92 )
A. that B. who C. from whom D. to whom
解析：本題考查定語從句中介詞加關系代詞的用法。根據句意“向某人求助”是turn to sb. for help，其中介詞to可提前，故答案為D。本句也可以如下表達：In the dark street, there wasn’t a single person (who/whom/that) she could turn to for help.)
4．After living in Paris for fifty years, he returned to the small town ____ he grew up as a child.
A. which B. where C. that D. when ( ’96 )
解析：本題考查關系代詞和關系副詞的用法，從句he grew up as a child不缺主語或賓語，排除關系代詞which和that，又因先行詞是表地點的，故答案為A。
5．Dorothy was always speaking highly of her role in the play, ____, of course, made the others unhappy. ( 2000 )
A. who B. which C. this D. what
解析：本題考查非限制性定語從句指代整個句子的用法，意為“老是自贊她在劇中表演的角色，這件事當然令他人不快。”指代前面所說的整句話，用which。故答案為B。從句中插入of course增加了考測難度，解題時可先把它忽略。
6．It was about 600 years ago ____ the first clock with a face and an hour hand was made. ( ’97 )
A. that B. until C. before D. when
解析：本題考查強調結構It was … that…，不管被強調的是時間還是地點，that不變，該結構與定語從句非常相似，注意區別。