复合句——定语从句is a beautiful girl. 形容词作定语Mary is a girl who has long hair. 句子作定语,修饰girl, 叫做定语从句先行词关系词定语从句关系代词关系副词when, why, wherewho, what,that, whom,whose在复合句中作定语，修饰主句中某一名词或代词的从句，叫做定语从句。
被修饰的名词或代词称为先行词。
定语从句的基本结构：主句（包括先行词）+ 关系词+ 定语从句。
其中对关系词的考查是中考重要的考点。
关系词作用：1.代替先行词;２．它还在定语从句中担任一定的成分;3. 同时连接先行词与它引导的定语从句。
（把主句和从句连起来）关系代词在定语从句中代替主句中的先行词，所以它在一般情况下都跟在先行词之后，而且它的人称、数必须和先行词一致。
关系词判断步骤:首先，要看先行词。
如果先行词是指人,关系代词可用who,that,whom,whose。
如果先行词指物,关系代词可用which或that;然后，要确定关系词在从句中的成分。
请看下表最后，定语从句谓语动词和先行词一致. 注:定语从句的时态不受主句的限制。
The woman who/that spoke at the meeting yesterday is my mother.①关系副词when状语时间where地点why原因②当关系代词which, that, whom在定语从句中作宾语时，也可以省略。
③在一般情况下，关系代词that和which(指物)或who(指人)可以互换，但在下列几种情况下，常只用that：△当先行词是不定代词时；△当先行词被形容词最高级或序数词修饰时；△当先行词被the very, the only等修饰时；△当先行词既有人又有物时。
△当主句已有疑问词who或which时，用that。
1.This is the most interesting story(__________ )I have ever heard.2.Here is something( _________) I will tell you.3.I can remember well t he persons and some pictures (___________) I see.4.Is it the one ___________ you want5. Who is the woman ___________was praised at the meeting④that和who不能紧跟在介词后作介词宾语，应使用关系代词whom，which置于介词后（但如果介词不前置仍放于句尾，则可用that 作引导词，而且可以省略。
）如：［正］This is the room (that/ which) the old man lives in.［正］This is the room in which the old man lives ［误］This is the room in that the old man lives在定语从句中作介词宾语，可以和介词一起放于先行词与定语从句之间，有时为了关系紧凑也可以将whom 与which 与先行词紧挨着书写，而将介词置于定语从句的后面，如：That was the man about whom they were talking.【策略指导】解决有关定语从句的题目时，首先要根据先行词确定好关系词，同时要记住一些特殊情况，这样才能做到万无一失。
定语从句的用法:1.当先行词是物时, 用which 或that引导.These are the trees _______________ were planted last year.which 指物，作主语或宾语(作宾语可省略,如介词提前则不能省)Is this the library (which/that) you borrow books fromIs this the library from which you borrow books2.当先行词是人时, 用who, whom, that引导.The man _____________is speaking at the meeting is a worker. ( )The boy who /that sits in front of me is Tom. ( )The man (whom/who/that) everyone likes is kind. (宾语)who, whom, whose, that用法区别.1.who 作定语从句的主语或宾语.作定语从句的宾语,在口语和非正式文体中常用who代替，可以省略.The woman (whom/who/that) they wanted to visit is a teacher.whom指人,作宾语(作宾语可省略,如介词提前则不能省)The man (whom/who/that) I talked to is Mr. Li.The man to whom I talked is Mr. Li.是代词的所有格形式, 它既可以代人也可以代物。
I know the girl whose mother is a teacher.【真题再现】1. He is the only student _____plays table tennis better than Jim.A. whyB. whereC. thatD. which解析：题干是一个含定语从句的复合句，先行词the only student是人，关系代词在从句中作主语，关系代词that可指代人。
why和where是可引导定语从句的关系副词，why表原因，先行词往往是表示原因的名词(reason等)，when 表时间，先行词往往是表示时间的名词(time, day, hour, year等)。
2. This is the dictionary _____ Mum gave me for my birthday.A. whichB. whatC. whoseD. whom解析：该定语从句中的先行词the dictionary是物，关系词在从句中作宾语，关系代词which可指代物。
关系代词whose可指代人（的），也可指代物（的），但在从句中常作定语；关系代词whom一般都指代人，在从句中常作宾语。
而what不引导定语从句。
3. This is the question _____ we are talking about now.A. thatB. whoC. whereD. when解析：在这里先行词是the question，指物，关系代词that可以指代物，而其他选项不可指代物。
4. Jack, there is someone in the office _____would like to speak with you.A. whoB. whichC. whomD. when解析：在这里先行词是someone，指人，关系代词在从句中作主语。
关系代词who和whom都可指代人，但whom在从句中充当宾语。
而关系代词which一般指代物。
5. We know Jackie Chan _____ movies are very popular with the young.A. whoseB. thatC. whoD. which解析：该句中先行词是Jackie Chan，关系代词在从句中作定语，选项中只有A项符合题意。
【现场练兵】用关系代词填空2.The boy ____________ is playing ping-pong is my classmate.3.The e-mail ___________ I received yesterday was from my sister.4.I hate people ______________ talk much but do little.5.The car _____________ my father bought last month is very beautiful.6.The man ______ hair is white is his grandfather.7. Is there a student _________ father is a business man8.This is the house in ________ we have lived for 10 years.9.I’ve never heard of the people and things ________ you talked about just now.10.My father and his teacher talked a lot about the persons and things ______ they couldn’t remember.11.Say all ________ you know.12.Is there anything ______ I can do for you单项选择( ) 1. —There are many volunteers _____are helping the children in Sichuan.—And most of them are college students.A. whichB. whenC. whoseD. who( ) 2. —Who is the woman _____ was talking to our English teacher—Oh! It’s Mrs. Baker, our new math teacher.A.whoseB. thatC. whomD. Which( ) place _______interested me most was the Children's Palace.A. WhichB. whereC. whatD. in which( ) you know the man _______A. whom I spokeB. to who spokeC. I spoke toD. that I spoke( ) is the hotel _______last month.A. which they stayedB. at that they stayedC. where they stayed atD. where they stayed( ) factory ______we'll visit next week is not far from here.A. whereB. to whichC. WhichD. in which( ) talked a lot about things and persons ________they remembered in the school.A. whichB. thatC. whomD. what( ) letter is from my sister, ______is working in Beijing.A. whichB. thatC. whomD. Who( )9. The dinner was the most expensive meal we __________.A. would haveB. have hadC. had never hadD. had ever had( )10. Do you know which hotel __________A. she is stayingB. she is staying inC. is she stayingD. is she staying in( )11. There is only one thing __________ I can do. A. what B. that C. all D. which。