定语从句是修饰名词或代词的，下面就是小阅给大家带来的中考英语语法专题详解十三：定语从句，希望能帮助到大家!
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一、什么是定语从句
定语从句(Attributive Clauses)在句中做定语，修饰一个名词或代词，被修饰的名词，词组或代词即先行词。定语从句通常出现在先行词之后，由关系词(关系代词或关系副词)引出。
二、定语从句的关系词
一般情况下，如果先行词表示人的名词或代词时，关系词应用who，whom或that。who和that在从句中可以作主语或宾语;whom在从句中作宾语。
whose在从句中常作主语的定语，通常指人，也可以指物，表示“谁的……”。。
先行词如果是表示物的名词或代词时，用that或which均可，但有些情况只能用that，有些情况只能用which。
三、在下列情况下，定语从句的关系代词多用that
1. 当先行词为all，something，anything等不定代词时用that。如：
You should tell me all(that)you have know about.
你因该把你所知道的情况告诉我。
Here is something that my father needs.
这正是我父亲所需要的东西。
2. 当先行词被every, no, some, any, little, much等修饰时，用that。如：
He has spent all the money that his father gave him.
他已经把父亲给他的钱都花掉了。
Tom tried every means that he could do to finish the job on time but he failed.
为了完成工作，汤姆想尽了一切办法，但他还是失败了。
3. 当先行词被序数词或形容词的最高级修饰时，用that。如：
This is the second letter that I received from my younger sister this month.
这是我这个月收到我妹妹的第二封信。
Gone with the Wind is one of the best films that I have ever seen.《乱世佳人》是我看过的最好的影片之一。
4. 先行词被only, very, same, last等词修饰时，用that。如：
This is the only book that you can read in these few days.
这是你最近几天能看的唯一一本书了。
That is the very magazine that he is looking for .
那正是他要找的那本杂志。
4. 在限制性定语从句中关系代词作表语时应用that。如：
The distance that you are from home is immaterial.
你离家的距离是微不足道的。
6. 当主语中已出现which而为了避免重复时使用that。如：
Which is the book that you need?
你需要的是哪一本书呢?
7. 当先行词既有人，又有物时，引导词只用that。如：
He can see two boys and some trees that are at a distance of five hundred meters.
他看见在五百米外有两个男孩和一些树。
四、在下列情况中则多用which
1. 非限制性定语从句多用which。如：
Canada, which is in North America, is the second largest country in the world.
位于北美洲的加拿大是世界第二大国。
2. 介词之后的定语从句多用which。如：
This is the stamp for which he is looking.
这正是他要找的那枚邮票。
3.“those+复数名词”之后的定语从句，用which。如：
A supermarket should keep a stock of those goods which sell well.
商场应储存一些销量好的商品。
4.定语从句离先行词较远时，用which。如：
My grandmother gave me a gift of great value on my birthday which I liked very much.
在我生日的那一天，我奶奶给了我一件非常珍贵的礼物，我非常喜欢它。
5. 先行词为代词that时，为避免重复，其后的定语从句的引导词多用which(非正式英语也用that)。如：
He told me that which I had told you before.
他告诉我的是以前我曾经给你说过的那件事。
五、在下列情况下，关系代词一般用who(指人)
1. 非限制性定语从句中，用who。如：
Lincoln,who was murdered at a theatre in Washington,D.C.,died on April 15,1865.
林肯在首都华盛顿的一家剧院被人暗杀，于1865年4月15日去世。
2. 当不定代词everybody(everyone)，anybody(anyone)，all one，ones等为先行词时，关系代词一般用who。如：
One who doesn’t work hard will never succeed.
不努力的人永远不会成功的。
Is there anybody who can swim across the river?
有人能游过这条河吗?
3.当先行词为those或people时，关系代词一般用who.
Those who want to see the exhibition must sign their names here.
要看这个展览的人必须在这里签名。
People who can see sometimes act just as foolishly.
有时候，眼睛看得见的人也会做同样的傻事。
4.在被分割开来的定语从句中，先行词为人时，关系代词一般用who，如：
I met a boy at the English Corner yesterday who can speak English fluently.
昨天，我在英语角上遇到一个能讲一口流利英语的男孩。
5.在以there be 开头的存在句型中，先行词为人，关系代词一般用who.如：
There was an old lady who wanted to see you at the gate just now.
刚才大门口有一位老妇人有事找你。