知识点总结
定语从句
定语从句在句中做后置定语，修饰名词或代词，被修饰的名词,词组或代词即先行词。引导定语从句的：
关系代词有：who, whom, whose, that, which等。
关系副词有：when, where, why等。
关系代词引导的定语从句
1）who, whom, that
Is he the man who/that wants to see you?
He is the man whom/ that I saw yesterday.
2) whose 用来指人或物，(只用作定语, 若指物，它还可以同of which互换）.
They rushed over to help the man whose car had broken down.
Please pass me the book whose (of which the) cover is green.
3）which, that
A prosperity which / that had never been seen before appears in the countryside.
The package (which / that) you are carrying is about to come unwrapped.
关系副词引导的定语从句
when, where, why
关系副词when, where, why的含义相当于"介词+ which"结构，因此常常和"介词+ which"结构交替使用，例如：
I still remember the day when(on which) I joined the Party.
Beijingis the place where (in which) I was born.
Is this the reason why (for which) he refused our offer?
限制性和非限制性定语从句
1) 定语从句有限制性和非限制性两种。限制性定语从句是先行词不可缺少的部分，去掉它主句意思往往不明确；非限制性定语从句是先行词的附加说明，去掉了也不会影响主句的意思，它与主句之间通常用逗号分开，例如：
This is the house which we bought last month.（限制性）
The house, which we bought last month, is very nice.（非限制性）
2) 当先行词是专有名词或物主代词和指示代词所修饰时，其后的定语从句通常是非限制性的，例如：
Charles Smith, who was my former teacher, retired last year.
My house, which I bought last year, has got a lovely garden.
This novel, which I have read three times, is very touching.
3) 非限制性定语从句还能将整个主句作为先行词。
He seems not to have grasped what I meant, which greatly upsets me.
Liquid water changes to vapor, which is called evaporation.
说明：关系代词that和关系副词why不能引导非限制性定语从句。
介词+关系词
1）介词后面的关系词不能省略。
2）that前不能有介词。
3） 某些在从句中充当时间，地点或原因状语的"介词+关系词"结构可以同关系副词when 和where 互换。
This is the house in which I lived two years ago.
Do you remember the day on which you joined our club?
as, which非限定性定语从句
由as, which 引导的非限定性定语从句，as和which可代整个主句，相当于and this或and that。As一般放在句首，which在句中。
As we know, smoking is harmful to one's health.
The sun heats the earth, which is very important to us.
as 和which在引导非限制性定语从句时，这两个关系代词都指主句所表达的整个意思，且在定语从句中都可以作主语和宾语。但不同之处主要有两点：
(1） as 引导的定语从句可置于句首，而which不可。
(2） as 代表前面的整个主句并在从句中作主语时，从句中的谓语必须是系动词；若为行为动词，则从句中的关系代词只能用which.。
as 的用法
1. the same… as；such…as 中的as 是一种固定结构, 和……一样……。
I have got into the same trouble as he (has).
2. as可引导非限制性从句，常带有'正如'。
As we know, smoking is harmful to one's health.
As is known, smoking is harmful to one's health.
As是关系代词。例1中的as作know的宾语；例2中，它充当从句的主语，谓语动词know要用被动式。
关系代词that的用法
1）不用that的情况
a) 在引导非限定性定语从句时。
(错)The tree, that is four hundred years old, is very famous here.
b) 介词后不能用。
We depend on the land from which we get our food.
We depend on the land that/which we get our food from.
2) 只能用that作为定语从句的关系代词的情况
a)在there be 句型中，只用that，不用which。
b)不定代词如：anything, nothing, the one, all, much, few, any, little等作先行词时，只用that，不用which。
c)先行词有the only, the very修饰时，只用that。
d)先行词为序数词、形容词最高级时，只用that。.
e)先行词既有人，又有物时。
举例：
All that is needed is a supply of oil.
Finally, the thief handed everything that he had stolen to the police.
误区提醒
1.关系代词、关系副词的误用；2.which前介词误用；3.该用that用which；4.非限制性定语从句引导词的误用
【典型例题】
1）Alice received an invitation from her boss, ___came as a surprise.
A. it B. that C. which D. he
解析：答案C. 此为非限定性从句，不能用 that修饰，而用which.，it 和he 都使后句成为句子，两个独立的句子不能单以逗号连接。况且选he句意不通。
2）I think you’re got to the point_______ a change is needed, otherwise you’ll fail.
A. when B. that C. where D. which
解析：错选A。当point 作先行词时，在逻辑上作定语从句抽象的地点状语，引导词选where。受汉语意思的干扰常错选when，翻译成时间“点”。正确答案C。
3）Many people who had seen the film were afraid to go to the forest when they remembered the scenes________ people were eaten by the tiger.
A. that B. by which C. which D. in which
解析：错选B。scene意思是“情景”，与之搭配的介词是in.故正确答案为D。
4）I hope________the little _____I have been able to do has been of some use.
A. that; that B./;by which C. what; what D./; with which
解析：错选D。第一空引导宾语从句，可选that，也可省略，关键看第二空；先行词the little为不定代词，后面的关系代词只能用that或省略。故正确答案为A。
