定语从句：在
复合句中修饰名词或代词的句子
先行词：被定语从句所修饰的词
He is a boy who is smart.
由
关系代词 引导
关系副词
关系代词：关系代词所代替的先行词是人或物的名词或代词，并在句中充当主语、宾语、定语等成分。关系代词在定语从句中作主语时，从句
谓语动词的人称和数要和先行词保持一致
These are students who won the first place last year.
I like the book which you bought yesterday.
Who
Whom 先行词为人
Whose
That
Which 先行词为物
（1）Who 与 Whom 以及 Whose 的区别
Who 在定语从句中做主语或宾语
Theman who is speaking at the meeting is a worker.
Whom 是 Who 的
宾格，所以在定语从句中充当宾语成分
Thewoman whom they wanted to visit is a teacher.
Whose 在定语从句中既可以指人也可以指物，要有“的”意思
Iknow the girl whose mother is a teacher.
Ihave a book whose cover is yellow.
（2）Which 和 That
两张先行词都是物，且在定语从句中充当主语或宾语，但that先行词也可以是人，且that充当定语从句宾语成分是可省略
Thisis a truck which / that is made in China.
I like the book (which / that) you bought yesterday.
Theman that is speaking at the meetingis a worker.
（3）只能用That的情况
1.
序数词或形容词最高级修饰先行词时
Tom is the cleverest boy that I have everknown.
This is the first play that I have seensince I came here.
2. 先行词被every, some, no, all, any, little,much等修饰时
I’ve read all the books that you lend me.
everything,something, nothing, all, anything, little, much等
不定代词作先行词时
Everything that we saw in thisfilm was true.
先行词被the only, the very, the same, the last修饰时
This is the very bookthat belongs to him.
主句已有who或which时
Who is the girl that is standingunder the tree?
Which is the machine that we used yesterday.
当先行词同时指人和物时
I’ve never heard of the people andthings that you talked about just now.
（4）As 和 Which 的区别
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
Hemarried her, as/which was natural.
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
As is known to all, China is a developing country.
关系副词：关系副词可代替的先行词是时间、地点或理由的名词，在从句中作状语。
Thisis the place where I was born.
Iremember the day when I first met him.
Canyou
tell me the reason why you lied to me?
关系副词 Where
When
why
关系副词和介词+关系代词（which）替换
When= On(in during…) Which
Why= forwhich
When= On(in in front of…) Which
I stillremember the day when I first met him.
I still remember the day on which I first methim.