定语从句三部曲1. 找出先行词；2. 确定先行词在从句中的成分：主语，宾语，状语；3. 选择正确的关系词。
几个关系代词的基本用法thatthat: 可指人或物；可作主语，宾语。
指人时，相当于who或whom；指物时，相当于whichA letter ________ is written in pencil is difficult to read.Do you know the gentleman _________spoke just now?What is the question ________they are talking about?Here is the man ______________you want to see.只能用that 不能用which的情况1.先行词为不定代词时：all, much, everything, anything, nothing, something, none, the one.2.先行词被only, any, few, little, no, just, very, one of等修饰时；3.先行词是序数词时或被序数词修饰时；4.先行词是最高级或被最高级修饰时；5.先行词既有人又有物时；6.先行词是数次时；(two, ten, a hundred)7.如果有两个从句，其中一个关系代词已用which ,另一个关系代词宜用that，以避免重复；8.疑问词是who或which，关系代词宜用that，以避免重复；9.主句是There be 结构，修饰其主句的定语从句宜用that 作关系代词；10.被修饰成分为表语时，或者关系代词本身是定语从句的表语时,该关系代词宜用that。
(主语+be+n. /adj.; 主语+系动词+adj.)即学即用1. The writer and his novel ____ you have just talked about is really well known .2. The most important thing ____ should be done right now is how to stop him from going on.3. The last place ____ we visited was the chemical works.4. There's nothing ____ can be said about it .5. This is the third film ____ has been shown in our school this term.1. Yesterday I caught two fish and put them in a basin of water. Now you can see the two ____are still alive.2. Who is the man ____ is standing at the gate?3. That's a good book _____will help you a lot.4. There is still a seat in the corner____ is still free.5. Edison built up a factory which produced things _____had never been seen before.逗号和介词后面不能用thatwhichwhich: 指物；可作主语，宾语，状语。
1. The book _____ was on the desk was bought by my father.2. The book _____ I bought yesterday is very interesting.3. The factory _____ his father works is far from here.只能用which不能用that 的情况：1. 介词后面只能用which；Is this the room in which Mr. White lives?2. 非限定性定语从句中。
More and more people are beginning to learn English, which is becoming very popular in our country.3.当关系代词后面带有插入语时；Here's the English grammar which, as I have told you, will help improve your English.4. 先行词是those+复数名词.A shop should keep a stock of those goods which sell best.who, whom, whosewho: 主格, 在从句中作主语，只可指人；whom: 宾格，在从句中作宾语，只可指人；whose: 属格，在从句中作定语，可指人也可指物。
（whose = of which或of whom）I like the students who work hard.All who heard the story were amazed.Chaplin, for whom life had once been very hard, was a success as an actor.A child whose parents are dead is called an orphan. I'd like a room whose window faces south.只能用who 不能用that 的情况1. 先行词为anyone, anybody, those, all, one, ones, they, he, people时；Anyone who failed to come to the meeting yesterday must give his reason .He who knows nothing but pretends to know everything is indeed a good-for –nothing.2. 在非限定性定语从句中；His mother, who loves him very much, is strict with him.3．在there be开头的句子中。
Here is a boy who wants to see you.WhenWhen 指时间，在定语从句中作时间状语。
其先行词是表时间的名词（如：time, day, week, year, month等）He came last night when I was out.We will put off the picnic until next week, when the weather would be better.when = 介词+which•I still remember the day when I first came to this school.(when= on which)•He came at a time when we needed him most.(when= at which)•We will never forget the year 1949, when the People's Republic of China was founded.(when= in which)比较•I still remember the day _________________my brother joined the army.•I still remember the days _____________we spent together.先行词是时间名词，但在定语从句中做宾语或主语时，先行词不能用when。
WhereWhere 指地点，在定语从句中作地点状语。
其先行词是表示地点的名词。
（如：place, school, factory, room等）This is the place where I was born.I live in the room where /in which he used to live.where = 介词+which•I recently went back to the town where I was born.(where = in which)•I would like to live in a country where there is plenty of sunshine.(where = in which)比较•The small mountain village ________we spent our holiday last month is now very famous.•This is the park _____________they visited last year.先行词是地点名词，但在定语从句中做宾语或主语时，先行词不能用where。
Why•Why 指原因，在定语从句中作原因状语。
先行词为reason 时，可用for which指代。
The reason why / for which / (that) he didn't attend the meeting was that he was ill.比较•I don’t believe the reason that/which he gave me.•Have you asked him the reason that may explain his success?当关系词在从句中作主语或宾语时，不能用why 引导。
先行词在从句中做状语时，关系词才可以用when，where和why。
补充当先行词为way时，定语从句常用that, in which,或how引导，that常可以省略。
This is the way that / in which I do such things.Please do the experiment in the way that/which I have shown you. (做宾语)as 的用法He was a foreigner, ____ I knew from his accent.A. thatB. asC. whereD. why①如为限制性的，多用于the same …as ; the same as；such …as …; as many/much as；so …as等结构中。