一 定语：修饰名词或代词的词、短语或从句称为定语。汉语中常用的表示。 定语主要由形容词担任。此外名词、代词、数词、副词、介词短语以及动词不定式（短语）、分词也可以做定语。a beautiful city; a bag full of money.注意：汉语的定语无论多长都放在被修饰词的前面，而英语中的定语则不然，是一个词时，放在被修饰词的前面， 若是两个以上的词组、短语或从句则放在被修饰词的后面，thirty women teachers ; his father; the girl in red. the boy from America Our monitor is always the first student to enter the classroom. falling leaves; fallen leaves; the boy playing basketball; the book bought by my mother; a reading room; a swimming poolHe is the man who you are looking for. 二：定义及相关术语1定语从句：修饰某一名词或代词的从句叫定语从句。定语从句一般紧跟在它所修饰的先行词之后。2先行词：被定语从句修饰的名词或代词叫先行词。3关系词：引导定语从句的词叫关系词。关系词有关系代词和关系副词。关系代词有that, which, who, whom, whose, as等；关系副词有when, where, why.1. I have an apple. An apple is red.I have an apple that/which is red. 先行词 关系代词2.I like some friends. Some friends like sports.I like friends who like sports. 先行词 关系代词3.I like music. The music is quiet. I like music that/which is quiet. 先行词 关系代词关系词通常有下列三个作用：A、引导定语从句，连接主从句；B、代替先行词；C、在定语从句中担当一个成分。（二）关系代词引导的定语从句1who 指人，在定语从句中作主语。The boys who are playing football are from Class One. Those who want to go to the museum must be at the school gate at 7 tomorrow morning. Yesterday I helped an old man who had lost his way. That is the teacher who teaches us physics. 2whom 指人，在定语从句中做宾语，常可省略。Mr Liu is the person ( whom ) you talked about on the bus. Li Ming is just the boy ( whom ) I want to see. The professor ( whom ) you are waiting for has come. The girl ( whom ) the teacher often praises is our monitor. 注意：关系代词whom 在口语或非正式文体中常可用who 来代替，也可省略。The man ( whom / who )you met just now is my old friend. 3Which 指物，在定语从句中做主语或宾语，做宾语时常可省略。Football is a game which is liked by most boys. He likes to read books which are written by foreign writers. The house which is by the lake looks nice. This is the pen ( which ) he bought yesterday. The film ( which ) they went to see last night was not interesting at all. 。 4That 即可指人，也可指物.。在定语从句中作主语或宾语，作宾语时常可省略。The number of people that / who come to visit this city each year reaches one million. Where is the man that / whom I saw this morning? The person that /whom you introduced to me is very kind. The season that / which comes after spring is summer. Yesterday I received a letter that / which came from Australia. 5Whose 即可指人，也可指物，在定语从句中做定语。I visited a scientist whose name is known all over the country. He has a friend whose father is a doctor. I once lived in the house whose roof has fallen in. 注意：指物时，常用下列结构来代替：The classroom whose door is broken will soon be repaired.The classroom the door of which is broken will soon be repaired.Do you like the book whose cover is yellow?Do you like the book the cover of which is yellow? （一）限制性定语从句中只能用that 引导定语从句的情况1当先行词是everything, anything, nothing (something 除外), all, none, few, little, some等不定代词时，或当先行词受every, any, all, some, no, little, few, much等不定代词修饰时。如：Have you taken down everything that Mr. Li said? There seems to be nothing that is impossible to him in the world. All that can be done has been done. 。There is little that I can do for you. He stayed in the library and looked up any information that they needed. 注意：当先行词指人时，偶尔也可用关系代词who，如：Any man that / who has a sense of duty wont do such a thing. All the guests that / who were invited to her wedding were important people. 2当先行词被序数词修饰时。如：The first place that they visited in London was the Big Ben. 3当先行词被形容词最高级修饰时。如：This is the best film that I have ever seen. 4当先行词被the very, the only修饰时。如：This is the very dictionary that I want to buy. After the fire in his house, the old car is the only thing that he owns. 注意：当先行词指人时，偶尔也可用关系代词who。如：Wang Hua is the only person in our school who will attend the meeting. 5当先行词前面有who, which等疑问代词时。如：Who is the man that is standing by the gate? Which is the T-shirt that fits me most? 6当先行词为人与物时。如：They talked about the persons and things that they remembered at school （三）关系副词引导的定语从句1 when 指时间，在定语从句中作时间状语。当先行词是表时间的名词，比如time, day, week, month, year等；且定语从句中缺时间状语时用when. 若先行词是表时间的名词，定语从句中缺主语或宾语时，用that/which引导。I still remember the day when I first came to this school. The time when we got together finally arrived. Do you remember the years when he lived in the countryside with his grandpare？Do you remember the days（that/which） we spent together last year? I will never forget the days when we spent our holidays together. I will never forget the days that / which we spent together. 2 where 指地点，在定语从句中作地点状语。若先行词是表地点的名词，比如park, city, farm, place等；且定语从句中缺地点状语时用where. 若先行词是表地点的名词，定语从句中缺主语或宾语时，用that/which引导。Shanghai is the city where I was born. 上海是我出生的城市。The house where I lived ten years ago has been pulled down. I visited the farm where a lot of cows were raised . Shanghai is the city (which/that) I want to visit.I know a place where we can have a picnic. I know a place which / that is famous for its beautiful natural scenery. 3 why 指原因，在定语从句中作原因状