语法专题：定语从句
定语从句和形容词是近亲，都喜欢修饰n.或pron.
He is a blalalala man.
He is a man who blalalala.
1.先行词：被定语从句修饰的n.或pron。
2.限制性定语从句和非限制性定语从句的区别。
Those who want to go, please sign their names here.(限制性定语从句)
This note was left by John, who was here a moment ago.（非限制性定语从句）
3.从句不完整，用关系代词；从句完整，用关系副词。
一．关系代词
1.That：
指人或物. 在定语从句中作主语，宾语，表语。作宾语时可省略。指人时，可与who, whom互换，指物时有时可与which互换。
I know the inventor that attended the meeting.（作主语）
He is the adviser（that）you are looking for. （作宾语）
【注意】
只能用that而不用which的情况：
第一种讲解方法：
（1）先行词为everything, something, anything, nothing,all, none, some,few, little,much,the one 等不定代词时；
I mean the one that was bought yesterday.
That is all that I have.
（2）先行词被形容词最高级或被only, any, few, little, no, all, one of 等修饰时；（如果先行词指人，可用关系代词who）
It is the most important taskthatshould be finished soon.
Don’t tell me any words that have nothing to do with me.
（3）先行词为数词或被序数词（含last）修饰时；
Look at these flowers. You can see the two thatyou gave me.
The first thing that my brother is going to do this afternoon is to write a letter.
（4）先行词被the only（唯一）, the very （正是），the same （同一个）等词修饰时。
This is the very book that I want.
（5）先行词中既有人又有物时：
We were deeply impressed by the teachers and schools that we had visited.
（6）先行词在主句中作表语，或关系代词在从句中作表语时；
It’s a book that will help you a lot.
My home town is no longer the place that it used to be.
第二种讲解方法：
两：先行词既有人又有物
代：先行词为everything, anything, nothing, all等指物的代词时
限：先行词被the only, the very, the last,以及much,little, few, no等限定词修饰时
形：先行词被形容词最高级修饰时
数：先行词为数量词
特：特殊疑问句
有：There/Here is句型中
重：多重定语从句中已经有了which，为避免重复
表：关系词在从句中作表语
序：先行词被序数词修饰
口诀：两代限形数，特有重表序
2.Which：
指物，在定语从句中作主语或宾语，作宾语时可省略。引导非限制性定语从句，可指代主句全句内容。
The tornado which happened last week was violent. （作主语）
He set the bird free, which made him happy. （作主语，指代主句全句）
Is that the entertainment program （which）you want to watch? （作宾语）
【注意】
只能用which不能用that 的情况：
（1）关系代词前有介词且指物时；
This is the room in whichLu Xun lived.
（2）非限制性定语从句中：
He has a daughter, whoworks in a hospital.
（3）先行词本身是that:
The clock is that which tells the time.
1. Who:
指人，在定语从句中作主语或宾语，作宾语时可以省略。
The man who is sitting in the front row is an architect.
The old man （who/whom）you saw yesterday is a thinker.
2. Whom:
指人，在定语从句中作宾语，可用who代替。
Is that the teacher （whom/who）you referred to ?
【注意】关系代词在从句中作宾语时常可省略，但介词提前时，关系代词只能用which或whom，且不能省略。
3. Whose:
既可指人可也指物，在定语从句中作定语。
They live in a house whose window faces south.
4. As:
既可指人也可指物，在定语从句中作主语，宾语或表语。
（1）引导限制性定语从句，用于such...as,so...as, the same...as,as many（或as much）...as 结构中：
The houses are sold at such a low price as people expected.
This is the same book as I read last week.
（2）引导非限制性定语从句，说明这个主句；从句的位置可在主句前，主句中或主句后，常用逗号和主句隔开。
As you know, our band was formed in a very unusual way.
As is often the case, Mary was late for school.
【补充】
as和which 的区别：
相同点：as, which 在非限制性定语从句中，都可指代整个句子，都可作主语，宾语，表语。
不同点：
1. 位置:as的位置灵活句首，句中都可以；which只放在句中。
2. 语义：as“正如”。
3. 固定搭配：as be done.
二．关系副词
1. Where:
当定语从句修饰地点名词，且关系词在从句中作地点状语时。相当于in/at/on...+which
Ancient China was a place where（=in which） states were often at war with each other.
【注意】先行词为表地点含义的抽象名词situation,case, position, point等，且从句缺少状语时，常用where引导定语从句。
It’s helpful to put children in a situation where they can see themselves differently.
2. when：
当定语从句修饰时间名词，且关系词在从句中作时间状语时。相当于in/at/on/during...+which,先行词常为day, week, time 等表时间的名词。
But it was a time when there were many great philosopher.
Between the two parts of the concert is an interval,when（=during which）the audience can buy ice-cream.
3. Why:
当先行词是the reason,且关系词在从句中作原因状语。相当于for which.
This is the reason why=（for which）I’ve changed so much.
【注意】
先行词reason如在从句中作主语或宾语，其后的定语从句用that 或which 引导。
The reason that/which he explained to me is unreasonable.
【误区警示】
先行词表示时间或地点时，关系词不总是用when或where。如果关系词在定语从句中作主语或宾语，就要用which 或that.
I will never forget the days that we spent together.
三．介词+关系代词
【注意】
有这种用法的关系代词主要是which 和whom
1. 一先：介词根据先行词的习惯搭配来确定。
I remember the day on which I joined the party.
the days during which I lived here.
the month in which I stayed here.
1.二动：介词根究从句中谓语动词的习惯搭配来确定。
This is the book on which I spent five dollars.
for which I paid five dollars.
from which I learnt a lot.
about which Tom often talks.
2.三意义：介词根据句子意义来确定。
This is the book from which I got the story.
【注意】
在非限制性定语从句中表“所有关系”或“整体中的一部分”时常用介词of。
The musicians were to play jokes on each other as well as play music, most of whichwas based loosely on the Beatles.
三．定语从句中的几个注意点
1.先行词为way:
（1）若引导词在从句中作主语，宾语或表语时，用关系代词which 或that 引导。
The way （that/which）you came up with at the meeting yesterday is well worth trying.
（2）若从句缺少方式状语，相当于“用这种方式/方法（=in this way）”
时，用that或in which 来引导，可省略。
Is this the way （that/in which）you deal with the garbage?
2.先行词为time:
（1）作“次数”讲，用that来引导。
I could hardly remember how many times （that） I’ve failed.
（2）作“一段时间”讲。
情况一：关系词在从句中作主语，宾语等，用that/which来引导。
I will never forget the time which/that we spent on the farm.
情况二：关系词在从句中作状语，用when或at/in/during which来引导。
He lived in a time when/during whichthere were no cars.
3.whose
可以与the +n.+of+which/whom互换。
We study in a room whosedoor faces south.=We study in a room the door of whichfaces south.
4.定语从句中的主谓一致
（1）关系代词在句中作主语，从句谓语动词单复数与先行词保持一致。
Children who are not active or whose diet is high in fat will gain weight quickly.
（2）先行词为one of +复数名词时，从句谓语动词用复数形式；先行词为the （only/very/right）one of +复数名词 时，从句谓语动词用单数形式。
That is one of the most expensive dictionaries that have come out in recent years.