定语从句是由关系代词和关系副词引导的从句,其作用是作定语修饰主句的某个名次性成分,定语从句分为限定性和非限定性从句两种.
一、 限定性定语从句
1. that即可代表事物也可代表人,which代表事物；它们在从句中作主语或宾语,that在从句中作宾语时常可省略关系词,which在从句中作宾语则不能省略.而且,如果which在从句中作“不及物动词＋介词”的介词的宾语,注意介词不要丢掉,而且介词总是放在关系代词which的前边,但有的则放在它原来的位置
2. which作宾语时,根据先行词与定语从句之间的语义关系,先行词与which之间的介词不能丢
3. 代表物时多用which,但在带有下列词的句子中用that而不用which,这些词包括all, anything, much等,这时的that常被省略
4. who和whom引导的从句用来修饰人,分别作从句中的主语和宾语,whom作宾语时,要注意它可以作动词的宾语也可以作介词的宾语
5. where是关系副词,用来表示地点的定语从句
6. when引导定语从句表示时间
〔注〕值得一提的是,表示时间“time"一词的定语从句只用when引导,有时不用任何关系代词,当然也不用that引导
By the time you arrive in London, we will have stayed there for two weeks.
I still remember the first time I met her.
Each time he goes to besiness trip, he brings a lot of living necessities, such as towers, soap, toothbrush etc.
7. whose是关系代词,修饰名词作定语,相当于所修饰成分的前置所有格
8. 当从句的逻辑主语是some, any, no, somebody, anybody, nobody, something, anything, everything或nothing时,常用there is来引导
二、非限定性定语从句：非限定性定语从句的作用是对所修饰的成分作进一步说明,通常和主句间用逗号隔开,将从句拿掉后其他部分仍可成立
1. which引导的非限定性定语从句来说明前面整个句子的情况或主句的某一部分
2. 在引导限定性定语从句时,that有时相当于in which, at which, for which或at which
Attitudes towards daydreaming are changing in much the same way that(in which) attitudes towards night dreaming have changed. 人们对白日做梦的态度正在改变,这与人们对夜间做梦的看法的变化有非常相似之处.
I like the music for the very reason that(for which) he dislike it. 我出于某种原因喜欢这种音乐,而他恰恰与我相反.
We arrived the day that(on which) they left. 刚好我们到的那天他们走了.
3. 有时as也可用作关系代词
4. 在非限定性定语从句中,不能用that,而用who, whom代表人,用which代表事物.
一.定语从句及相关术语
1.定语从句：修饰一个名词或代词的从句称为定语从句,一般紧跟在它所修饰的先行词后面.
2.关系词：引导定语从句的关联词成为关系词
关系词有关系代词和关系副词.关系代词有that, which, who, whom, whose, as等；关系副词有where, when, why等.
关系词常有3个作用：1,引导定语从句.2,代替先行词.3,在定语从句中担当一个成分.
二.关系代词引导的定语从句
1.who指人,在从句中做主语
(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,在定语从句中充当宾语,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：关系代词whom在口语和非正式语体中常用who代替,可省略.
(3) The man who/whom you met just now is my friend.
3. which指物,在定语从句中做主语或者宾语,做宾语时可省略
(1) Football is a game which is liked by most boys.
(2) This is the pen (which) he bought yesterday.
4. that指人时,相当于who或者whom；指物时,相当于which.在宾语从句中做主语或者宾语,做宾语时可省略.
(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,在定语从句中做定语
(1) He has a friend whose father is a doctor.
(2) I once lived in a house whose roof has fallen in.
whose指物时,常用以下结构来代替
(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.介词+关系代词引导的定语从句
关系代词在定语从句中做介词宾语时,从句常由介词+关系代词引导
(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 talked about.
(6) We’ll go to hear the famous singer about whom we have often talked.
注意：1. 含有介词的动词短语一般不拆开使用,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. 若介词放在关系代词前,关系代词指人时用whom,不可用who或者that；指物时用which,不能用that；关系代词是所有格时用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. “介词+关系代词”前可有some, any, none, both, all, neither, most, each, few等代词或者数词
(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．关系副词引导的定语从句
1. when指时间,在定语从句中做时间状语
(1) I still remember the day when I first came to the school.
(2) The time when we got together finally came.
2. where指地点,在定语从句中做地点状语
(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,在定语从句中做原因状语
(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：关系副词引导的从句可以由“介词+关系代词”引导的从句替换
(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.
五．限制性定语从句和非限制性定语从句
限制性定语从句 非限制性定语从句
形式上 不用逗号和主句隔开 用逗号和主句隔开
意义上 是先行词不可缺少的定语,不能删除 是对先行词的补充说明,删除后意思仍完整
译法上 翻译成先行词的定语,“…的…” 通常翻译成主句的并列句
关系词的使用上 A．做宾语时可省略 B.可用that
C．可用who代替whom A．不可省 B.不用that
C.不用who代替whom
限制性定语从句举例：
(1) The teacher told me that Tom was the only person that I could depend on.
(2) China is a country which has a long history.
非限制性定语从句举例：
(1) His mother, who loves him very much, is strict with him.
(2) China, which was founded in 1949, is becoming more and more powerful.
要注意区分以下几个句子的不同
(1) His brother who is now a doctor always encourages him to go to college.
他那当医生的哥哥常鼓励他要考上大学.（他还有其他的哥哥）
(2) His brother, who is now a doctor, always encourages him to go to college.
他的哥哥是当医生的,常鼓励他要考上大学.（他只有一个哥哥）
难点分析
（一）限制性定语从句只能用that的几种情况
1．当先行词是anything, everything, nothing (something 除外), few, all, none, little, some等代词时,或者是由every, any, all, some, no, little, few, much等修饰时
(1) Have you taken down everything that Mr. Li has said?
(2) There seems to be nothing that seems impossible for him in the world.
(3) All that can be done has been done.
(4) There is little that I can do for you.
注意：当先行词指人时,偶尔也可以用who
(4) Any man that/.who has a sense of duty won’t do such a thing.
2. 当先行词被序数词修饰
(1) The first place that they visited in London was the Big Ben.
3. 当先行词被形容词最高级修饰时
(1) This is the best film that I have seen.
4. 当形容词被the very, the only 修饰时
(1) This is the very dictionary that I want to buy,
(2) After the fire in his house, the old car is the only thing that he owned.
当先行词指人时,偶尔也可以用who
(3) Wang Hua is the only person in our school who will attend the meeting/
5. 当先行词前面有who, which等疑问代词时
(1) Who is the man that is standing there?
(2) Which is the T-shirt that fits me most?
6. 当先行词既有人,也有动物或者物体时
(1) Can you remember the scientist and his theory that we have learned?
（二）关系代词as和which引导的定语从句
as和which引导非限制性定语从句,有相同之处也有不同之处.具体情况是：
1．As和which都可以在定语从句中做主语或者宾语,代表前面整个句子.
(1) He married her, as/which was natural.
(2) He was honest, as/which we can see.
2. as 引导非限制性定语从句,可放在主句之前,或者主句之后,甚至可以切割一个主句；which引导的非限制性定语从句只能放在主句之后.另外,as有“正如……,正像……”的意思
(1) As is known to all, China is a developing country.
(2) He is from the south, as we can see from his accent.
(3) John, as you know, is a famous writer.
(4) He has been to Paris more than several times, which I don’t believe.