1.定语从句: 1) 定语从句的定义在复合句中，修饰名词或代词的从句叫做定语从句。
被定语从句所修饰的词叫先行词。
引导定语从句的词叫关系词。
关系词包括关系代词who(宾格whom,所有格whose),that, which 和关系副词where, when, why 等。
The boy who is wearing a black coat bought a dictionary yesterday.The noodles that（which）my mother cooked were delicious.The school where I learned judo was very large.I remember the day when our band was formed.I don’t know the reason why she got so angry this morning.2) 定语从句的种类：定语从句可以分为限定性定语从句和非限定性定语从句。
(1)限定性定语从句：它是先行词在意义上不可缺少的定语，如果去掉，主句的意思就不完整或失去意义。
这种从句与主句的关系十分密切，书写时不可用逗号分开。
如果关系代词在限定性定语从句中作宾语，关系代词通常可以省略。
Do you know the girl who just came in?Shanghai is a city（that）I’ve always wanted to visit.Her sister married a man (who/whom/that) she met on a plane.The time when I first met Mr. White was a very difficult period of my life.(2)非限定性定语从句：它只是对先行词作附加补充说明，如果去掉，主句的意思仍然清楚完整。
这种从句与主句的关系不是很密切，书写时往往用逗号分开。
非限定性定语从句一般不用that 引导，而且不可以省略关系词。
The old woman, who lives on her own, has a cat for company.Lori is going to marry Mark, whom she does not love.Beijing, which is the capital city of China, is a very beautiful city.3) 关系代词的用法：在定语从句中，关系代词起着连接主句与从句，指代先行词和在从句中作句子成分的三重作用。
关系代词的选用取决于主句中的先行词以及关系代词在从句中作何种成分。
一．关系代词who, whom 的用法（1）who 可以代替人（即它的先行词必须是人），在从句中担任主语，往往也可以代替在从句中担任宾格的whom,但它的前面不能有介词，如果带介词则必须用宾格whom，即“介词+whom”. E.g. Jonny is a person who always has novel ideas.The girl who the first prize in the contest is from Zhejiang.The person who/whom you just talked to is Mr. Depp.---The person to whom you just talked is Mr. Depp. (介词to提到定语从句前，只能用whom.)We’ll go to the hospital to see the patients, most of whom are children.(whom 前常用表示数量的词none/neither/both/each/all of…)(2)在定语从句中，who, that 指人时可以通用，但在下列情况下用who,而不用that.A) 先行词是one, ones, anyone 时，宜用who.One who has nothing to fear for oneself dares to tell the truth.The ones who flatter me don’t please me. Anyone who laughs last laughs best.Anyone who fails to finish the task given should be criticized.B) 先行词为those 时，宜用who. Those who want to go to the Great Wall sign up here.No words are strong enough to express our thanks to those who worked hard to rescue survivors in the earthquake.C) 当先行词有较长的后置定语时，宜用who.I met a girl in the street yesterday who grew up in Yunnan province.D) 一个句子中带有两个定语从句时，其中一个定语从句的关系代词时that，另一个宜用who. E.g. The boy that you met last night is the group leader who studies very hard.E) 在there be 开头的句子中，事宜用who.There is a young man who wants to see your father. There was a king who was kind to his people.There are many old men who are against this plan.二．关系代词whose 的用法：关系代词whose 是关系代词who 的所有格形式，它既可以代人，也可以代物。
当whose 代物时，相当于of which. Whose 引导的定语从句既可以是限定性定语从句，也可以是非限定性定语从句。
Do you know Peter whose father happens to be working in your company?The tourist wanted to book a room whose window faces south.=The tourist wanted to book a room the window of which faces south.=The tourist wanted to book a room . The room’s window faces south.We went to see our teacher Miss Styles, whose husband lost his life in the earthquake.Xi’an, whose walls remain as good as before, is one of the few cities with city walls.三．关系代词that, which 的用法（1）在限定性定语从句中指代物时，which 和that 一般可通用。
The new house that/which I has just bought is about six miles away.They planted some trees that /which didn’t need much water.(2) 限定性定语从句中只用that 而不用which 的情况。
A）先行词有形容词最高级修饰时This is the best way that has been used against pollution.Polly is the most direct young woman that I have ever come across .B) 先行词有序数词修饰时This is the third time that they have met.The very first time that Lester saw the film, he made up his mind to become a doctor.C)主句已有疑问词who 或which 时Which of the car s that are in front of the hotel belongs to you?Who is the man that is sitting by the lake ?D) 先行词既有人又有物时He talked about the schools and teachers that he had visited.The bike and his rider that had run over an old man were taken to the police station.E) 先行词为all, much, few, little, something, everything, anything, nothing, none 等不定代词时It’s easy to do the repair. All that you need is a hammer and some nails.We haven’t got much that we can offer you.I’d like to tell you something that will make you surprised.F) 先行词前面有the very, the only, the same, any, few, little, no, all, one of 等词修饰时This is the very room that I slept in that evening.The only thing that we can do is to give you some money.Li Ming is the only one that wants to be a teacher.G) 有两个定语从句，其中一个关系代词以用which,另一个宜用thatEdison built up a factory which produced things that had never been seen before.(3) 只用which 而不用that 的情况A) 引导非限定定语从句时The fish, which I bought this morning, is very fresh.My house, which I bought two years ago, has got a lovely garden.Jim passed the driving test, which surprised everybody in the office.Helen was much kinder to her youngest son than to others, which , of course, made the others envy him.The factory produces half a million pairs of shoes every year, most of which are sold abroad.(which 前常用none/neither/most/both/each/all/a little of等词修饰)B）在限定性定语从句中，关系带词前有介词时I was put in a position in which I had to accept I was less important.This is the hotel in which you will stay.= That’s the hotel (which/that) you will stay in.(此句中，如果介词in 放在句子的后面，那么关系代词既可用which,也可用that,还可省略。
