定语从句讲解一．基本介绍①功能：相当于adj,修饰名词或代词，在句中作定语。
②位置：被修饰词之后③先行词：被定语从句修饰的词④关系词：连接先行词与从句的词称为关系词。
⑤定语从句结构：先行词+关系词+定语从句。
⑥定语从句分类限定性定语从句：从句对先行词进行必要的描述或说明，对先行词起修饰限定作用，从句与先行词紧密相连，缺少它则句义显得不完整，一般不用逗号隔开。
非限定性定语从句：对先行词进行补充说明，解释，它与先行词关系松散，用逗号隔开。
1、The man who gave me this book is Tom .(限定性)2、Tom,who is reading a book ,is my classmate (非限定性)二.定语从句的关系词关系词的作用：1.引导主从句2. 代替先行词指人：who、whom、whose、that关系代词指物：which、that、whose关系词时间：when关系副词地点：where原因：why确定关系词的步骤：1. 先看先行词，区分人或物；2.分析从句成分是否完整；3.缺啥补啥关系词选择练习1. I like the girl ________lent me a book yesterday.2. I know the girl ________ the teacher is speaking to.3. I know the girl __________ the teacher is speaking .4. This is a plant _______ grows in the north.5. He doesn’t seem to be the man _________he was ten years ago.6. Everyone helps the child _________ parents are dead.7. The building, _________roof is white, is our teaching building.8. The building, _________ _________ the roof is white, is our teaching building.9.I’ll never forget the time _________ (during which ) we worked on the farm.10. I still remember the day ________ I spent with my grandma.11. This is the house _________ he has lived for 20 years12. This is the house_________ he has lived in for 20 years.13. This is the school _________ we study every year.14. This is the school _________we visited yesterday. .15. That’s the reason _________ he didn’t come to scho ol.16. I don’t believe the reason________ he gave me.答案1.who/that2. whom/who/X3. to whom4.that/which5. that6.whose7. whose8. of which9. when 10. that/which/X 11. where 12.that/which/X 13. where / in which 14.that/which/x 15. why/for which 16.that/which/x三. 特殊用法：that 与which的区别☆常用that不用which的情况1、当先行词是all, everything, anything, nothing, much, little, none, one等不定代词时，只用that。
歌诀助记：不定代词这路货，全用that准没错。
Pay attention to everything that I do.2、当先行词被序数词或形容词最高级修饰时，只用that。
歌诀助记：先行词前被限定，千万不要用which。
This is the best novel (that)I have read.3、如果出现两个或两个以上的先行词，并同时兼指人和物时，关系代词用that。
歌诀助记：两项并列人与物，引导定从用that。
They were talking about the person and things that they remembered in school.4、当先行词被the only, the last, the way, the same等修饰时。
This is the last time that I shall give you a lesson.5、在疑问词which开头的特殊疑问句中，为了避免重复只用that。
Which of the students that knows something about history.☆常用which，不用that的情况1、引导非限制性定语从句。
Football, which is an interesting game, is played all over the world.2、放在介词后作宾语时（介词+关系代词结构中）。
Language is the most important tool without which people can't communicate with each other.3、先行词为thatWe have that which we need.练习1. Everything ______ can be done has been done.2. There are few books ____ we can read.3. This is the only food ____ I can find for you.4. This is the last thing _______ I’ll do.5. This is the most interesting film ______ I have ever seen.6. They talked for about half an hour of things and persons ______ they remembered in the school.7. All the books _____ he has translated are very popular here.四. 非限定性定语从句关系代词在非限定性定语从句中的用法。
指人做主语用who,作宾语用whom ，指地点用where，指时间when，指物只用which，不能用that，作定语用whose。
e.g. He didn’t see the film, which was very interesting .(不用that)一. as 引导的限制性定语从句A . such ….as 和the same…as 的用法such ….as：像….一样的，像…..之类；the same…as：和…..同样的在这两个句型中，as是关系代词，such和same 作定语，修饰主语里的某个名词（或代词），这个名词是由as引导的定语从句的先行词，as在从句中可担任主语、宾语或表语。
Eg：We have found such materials as are used in their factory.( 在从句中作____语)I seldom give my students such a difficult problem as they cannot work out.（在从句中作_____语）The result is not the same as they had expected.( 在从句中作_____语)重点比较:the same …as…和the same …that…the same…as…:和…..相同（代指同类事物）；the same …that…：和….相同（代指同一事物）两者都引导定语从句。
as 从句中说明的名词与the same 修饰的名词是同一类，而非同一个。
that从句中说明的名词与the same 修饰的名词是同一个。
Eg：He is reading the same book that you bought yesterday.He is reading the same book as you bought yesterday.This is the same pen that I lost. =This is the pen that I lost.(指同一支笔)This is the same (kind/type/sort) of pen as I lost.（指同类型的笔，但并不是我丢失的那一支）（二）as 和which引导的非限制性定语从句as 可以像which一样引导非限制性定语从句，用来代表整个句子的内容，它的先行词可以是名词，也可以是不定式短语或整个句子。
as 在从句中作主语、宾语和表语。
重点比较：as 和which 引导的非限制性定语从句的联系和区别(1)含义as 正如，像which 无意义(2)位置as 位置灵活，句首，句中或句末which 句末(3)as 常见搭配As we know As has been said before 如上所述As is known to all As is often the case 像通常那样As is reported As was expected 正如预料的那样(4) which 补充说明从句否定时Eg：As we all know, he has passed the exam.He, as we all know, has passed the exam.As is known to all, he has passed the exam.He broke the glass which made his mother angry.(三)非限定性定语从句和并列句的比较There are 45 students in my class, most of _______are girls.There are 45 students in our class, and most of _______are girls.五. 同位语从句与定语从句区别1、同位语从句和定语从句结构相似，通常位于某一名词或代词之后，但两者存在明显区别：同位语从句对名词性成分加以补充说明，是该名词性成分具体内容的体现（相当于名词的作用）。