修饰名词代词的从句叫定语从句,被修饰的名词或代词叫先行词,引导定语从句的有关系代词who,whom, whose, which, that等关系副词where,when,why 等, 关系代词和关系副词在定语从句中担任句子成份
whom, which用作介词宾语时,介词可放在 whom、which之前,也可放在从句原来的位置上;但在含有介词的动词固定词组中,介词只能放在原来的位置上。
如: He is the very person whom we must take good care of
1.由who引导的定语从句中, who用作主语如:This is the boy who often heips me.
2.由whom引导的定语从句中,whom用作宾语
如: The man whom you are waiting for has gone home.
3.由whose 引导的定语从句中， whose用作定语
如:Do you know the girl whose skirt is white?
4.由which 引导的定语从句中, which用作主语或谓语动词的宾语或介词的宾语如:The room in which there is a machine is a work shop. The river which is in front of my house is very clean. This is the pen which you want.
当定语从句中含有介词,介词放在句末时, who, that, which可省略,但介词在关系代词前时,只能用“介词+which/whom"结构例如:
①This is the house in which we lived last year.
这是我们去年居住的房子
②Please tell me from whom you borrowed the English novel.请告诉我你从谁那借的这本英文小说
as 引导非限制性定语从句时，可放置主句之前或之后，而which只能放先行词之后，此外as有正如/好像的意思
As we had predicted, he did nothing at all.
正如我们所预料那样,他根本什么也没有做
The aged people has been increasing in recent years, which makesthe country get into the aged society rapidly.
近些年老龄人口的持续增长导致国家加快步伐进入老龄社会.
关系副词when
when既可引导限制性定语从句,又可引导非限制性定语从句。先行词是时间名词,在从句中充当时间状语,相当于“介词+which”
Can you tell me the time when the film will start?
Can you tell me the time at which the film will start?请告诉我电影什么时候开始好吗?(限制性定语从句)
Iwill never forget the day, when I joined the Party. l will never forget the day, on which I joined the Party.我入党的那一天,我永远不会忘记。(非限制性定语从句)
关系副词where
where 既可引导限制性定语从句,又可引导非限制性定语从句,先行词是地点名词,在从句中充当地点状语，相当于:“介词+which”
This is the school where I studied a few years ago.
This is the school in which l studied a few years ago. 这就是我几年前所在读书的学校
Let's go to the concert, where you will find much fun. Let's go to the concert, in which you will find much fun. 我们去音乐演唱会吧,在那里你会找到很大的乐趣。
关系副词why
why只能引导限制性定语从句,先行词只有reason 一词，在从句中充当原因状语,相当于:"for + which”.
Do you know the reason why he is not here now?
Do you know the reason for which he is not here now?你知道他还没有来这儿的原因吗?
关系副词that
that只能引导限制性定语从句,充当关系副词时,其作用相当于:“介词+关系代词"，在从句中充当时间、地点、方式、原因状语等
1.在定语从句中作时间状语,先行词有:each time, every time, anytime,
the first time, the moment, the minute, the hour, etc.但that往往省略
Each time (that)l meet him, he will smile and say"hello”
每次我会见他时,他都会笑着说"喂,你好!"
2.在定语从句中作方式状语,先行词是way
Can you show me the way (that) you solve the problem like this?
请告诉我你解决这类问题的方法好吗?
3.在定语从句中作原因状语,先行词只有reason一词
l don't know the reason(that) he has left school now.
我不知道他辍学的原因
4.在定语从句中做其他状语,先行词如price, speed等
l think the price(that) she sells her apple is too high. (that = at which)我认为她卖苹果的价格太高了。
1.that既可以用于指人,也可以用于指物,在从句中作主语或宾语,作主语时不可省略,作宾语时可省略
①Mary likes music that is quiet and gentle.玛丽喜欢轻柔的音乐(that 作主语)。 ②The coat(that)I put on the desk is blue.
我放在桌子上的那件外套是蓝色的(that 作宾语)
2. which 用于指物，在句中作主语或宾语,作主语不可省略,作宾语可省略
①The building which stands near the train station is a supermarket.
位于火车站附近的那座大楼是一家超市(作主语) ②The film (which) we saw last night was wonderful.我们昨天晚上看的那部电影很好看(作宾语)
3.who, whom都用于指人, who用作主语, whom用作宾语,在口语中，有时可用who代替 whom,也可省略
①The girl who often helps me with my English is from England.
经常在英语方面帮助我的那个女孩是英国人(作主语)
② Who is the teacher (whom)Li Ming is talking to?正在与李明谈话的老师是谁?(作宾语)
限制性定语从句作定语修饰主句的某个名词性成分，相当于形容词，所以又称为形容词性从句，一般紧跟在它所修饰的先行词后面
The room whose window faces south is mine.=The room of which the window faces south is mine. 窗户朝南的那间房间是我的。 The whole city, 75% of whose factories and buildings were gone, lay in ruins. 整座城市躺在废墟中，其中百分子75的工厂和大楼消失不见了。 Our company has 2000 workers, of whom two thirds/ two thirds of whom are women. 我们公司有2000工人，三分之二是女工。 Those who were trapped under the ruins finally got rescued那些被困在废墟里的人已经得救了。
非限制性定语从句在句中主要起补充说明作用，与主句之间往往有逗号隔开，独立存在，不会影响整个句子的意思。
Our guide,who was a French Canadian，was an excellent cook.
我们的向导，一个法裔加拿大人，擅长于烹调。
Then he met Mary，who invited him to a party.
后来他遇到玛丽，玛丽邀请他去参加晚会。
My gardener，who is very pessimistic，says that there will be no apples this year.
我家的园丁非常悲观，他说今年将不结苹果。
关系词只能用which,而不用that的情况
(A).先行词为 that, those 时
What's that which is under the desk?
在桌子底下的那些东西是什么?
(B).关系代词前有介词时
This is the room in which he lives.
这是他居住的房间
(C).引导非限制性定语从句
Tom came back, which made us happy.
汤姆回来了,这使我们很高兴
必须用that引导定语从句,而不用which的情况
(1)先行词是不定代词 all, few. little, much,something, nothing,anything等
All that we have to do is to practise English. 我们所要做的就是练习英语。 ls there anything that you want to buy in the shop?
你在商店里有什么东西要买吗?
(2)先行词被序数词或形容词最高级所修饰,或本身是序数词、基数词、形容词最高级时
The first letter that I got from him will be 我收到的第一封信是 He was the first person that passed the exam.
他是第一个通过考试的人。
(3)先行词被all,any, every,each, few, little,no, some等修饰
I've eaten up all the food that you gave me. 我把你给我的食物都吃光了。
(4)先行词被the only, the very, the same, the last修饰时
This is the same bike that I lost.
这就是我丢的那辆自行车。
He is the only person that I want to talk with. 他是我唯一想谈话的人。
(5)先行词既有人又有物时
They talked about persons and things that they met 他们谈论他们遇到的人和事 I can remember well the persons and some pictures that I sawin the room.
我能清楚记得我在那个房间所见到的人和一些照片。
(6)主句是there be结构,修饰主语的定语从句
There is a book on the desk that belongs to Tom.桌子上那本书是汤姆的
(7)当句中已有who时,为避免重复
Who is the man that is giving us the class?
