引导定语从句的关联词称为关系词，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，绝对没有what；关系副词有where, when, why等。关系词常有3个作用：①连接作用，引导定语从句。②代替主句中的先行词，甚至可能是主句中的一部分或者整个主句。③在定语从句中充当一句子成分。注：关系代词有主语、宾语之分。一般whom作为宾语。关系代词在从句中作主语，宾语，表语，定语等，关系副词在从句中作地点状语，时间状语，原因状语等。
先行词 被定语从句修饰的名词、代词称为先行词。
关系代词所代替的先行词是人或物的名词或代词，并在从句中充当主语、宾语、定语等成分。关系代词在定语从句中作主语时，从句谓语动词的人称和数要和先行词保持一致。
who, whom, that
这些词代替的先行词是人的名词或代词，who做主语指人，whom作宾语指人，that既可作主语又可作宾语（作宾语可以省略），可以指人也可以指物。在从句中所起作用如下： (1) Is he the man who/that wants to see you? 他就是想见你的人吗？（who/that在从句中作主语） (2) He is the man whom/ that I saw yesterday. 他就是我昨天见的那个人。（whom/that在从句中作宾语）
Whose 用来指人或物(只用作定语, 若指物，它还可以同of which互换，指人的时候也可以用of whom 代替） (1) They rushed over to help the man whose car had broken down. 那人车坏了，大家都跑过去帮忙。(2) Please pass me the book whose (of which) color is green. 请递给我那本绿皮的书。
which, that
它们所代替的先行词是事物的名词或代词，在从句中可作主语、宾语等，作宾语时可以省略，例如： (1) A prosperity which / that had never been seen before appears in the countryside. 农村出现了前所未有的繁荣。（which / that在句中作主语） (2) The package (which / that) you are carrying is about to come unwrapped. 你拿那个包裹快要散开了。(which / that在句中作宾语） 4、 as as 可以做主语，也可以作宾语，作宾语时可以省略，指人或者物。常与such as,the same as等短语连用。
编辑本段限定性定语从句
关系代词
关系代词：在句中作主语、宾语或定语 1. that既可代表事物也可代表人，which代表事物；它们在从句中作主语或宾语，that在从句中作宾语时常可省略关系词，which在从句中作宾语也可以省略。[eg：This is the book （which）you want.] 2. 如果which在从句中作“不及物动词＋介词”的介词的宾语，注意介词不要丢掉，而且介词总是放在关系代词which的前边，但有的则放在它原来的位置 3. 代表物时多用which，但在下列情况中用that而不用which： a)先行词是anything, everything, nothing , none等不定代词时； b)先行词由every, any, all, some, no, little, few, much等修饰时，这时的that常被省略； c)先行词前有序数词或被形容词最高级修饰时； d)先行词中既有人又有物时； e)整个句中前面已有which，who,that时； f)当先行词为物并作表语时； g)先行词为one时； h)先行词同时又被the only,the very,the same修饰时； 4. who和whom引导的从句用来修饰人，分别作从句中的主语和宾语，whom作宾语时，要注意它可以作动词的宾语也可以作介词的宾语 5. whose是关系代词，修饰名词作定语，相当于所修饰成分的前置所有格.它引导的从句可以修饰人和物, 当它引导的从句修饰物体时, 可以与 of which 调换,表达的意思一样。
关系副词
关系副词：在句中作状语 关系副词=介词+关系代词 why=for which where=in/ at/ on/ ... which (介词同先行词搭配) when=during/ on/ in/ ... which (介词同先行词搭配) 1. where是关系副词，用来表示地点的定语从句。 2. when引导定语从句表示时间〔注〕值得一提的是，表示时间“time"一词的定语从句只用when引导，有时不用任何关系代词，当然也不用that引导。 By the time you arrived in London, we had stayed there for two weeks. 到你到达伦敦的时候，我们在那里已经待了两个星期。 I still remember the first time I met her. 我仍然记得我第一次见到她。 Each time he goes to business trip, he brings a lot of living necessities, such as towels, soap, toothbrush etc。 每一次他去出差，他带来了生活必需品，如毛巾，肥皂，牙刷等，很多。 3. 当从句的逻辑主语是some, any, no, somebody, anybody, nobody, something, anything, everything或nothing时，常用there is来引导 There is somebody here who wants to speak to you. 这里有人要和你说话。 非限制性定语从句的作用是对所修饰的成分作进一步说明，通常是引导词和先行词之间用逗号隔开，将从句拿掉后其他部分仍可成立
编辑本段非限制性定语从句
1. which引导的非限定性定语从句作用是说明前面整个句子的情况或主句的某一部分 2.当先行词是专有名词、物主代词或指示代词所修饰时，其后的定语从句通常是非限制性的，例如： Charles Smith, who was my former teacher, retired last year. 查理·史密斯去年退休了，他曾经是我的老师。 My house, which I bought last year, has got a lovely garden. 我去年买的的那幢房子带着个漂亮的花园。 This novel, which I have read three times, is very touching. 这本小说很动人，我已经读了三遍。 3.非限定性定语从句可将整个主句作为先行词, 对其进行修饰, 这时从句谓语动词要用第三人称单数，例如： He seems not to have grasped what I meant, which greatly upsets me. 他似乎没抓住我的意思，这使我心烦。 Liquid water changes to vapor, which is called evaporation. 液态水变为蒸汽，这就叫做蒸发。 4. 有时as也可用作关系代词 5. 在非限定性定语从句中，不能用关系副词why和关系代词that，而用who, whom代表人，用which,whose代表事物，如果需要用why，可用for which代替.； p.s: which引导的非限制性定语从句其后不可省略成分，as可以
编辑本段关系代词引导的定语从句
who指人在从句中做主语
(1) The boys who are playing football are from Class One. 在踢足球的男孩们是一班的. (2) Yesterday I helped an old man who lost his way. 昨天，我帮助了一个迷路的老人.
whom指人
在定语从句中充当宾语，常省略。（注：who和whom已无太大区别，基本可以通用。区别是who可以做主语而whom不可以，whom前可以加介词如to whom，但是who不可以） (1) Mr. Liu is the person (whom) you talked with on the bus. 刘先生就是在公交车上和你聊天的那个人. (2) Mr. Ling is just the boy(whom)I want to see. 凌先生恰巧就是我想见的那个男孩. (3) The man who/whom you met just now is my friend. 你刚刚见到的那个人就是我的朋友. 注意：关系代词whom在口语和非正式语体中常用who代替，可省略。 如果在从句中做宾语,就用whom或who.比如: He is the man whom/who I talk to. 他就是那个和我聊天的男人. 如果是在从句中作主语就只能用who.比如: He is the man who has an English book. 他就是那个有英语书的男人.
whose通常指人也可指物
在定语从句中做定语。 (1) He has a friend whose father is a doctor. 他有一个朋友的父亲是医生. (2) I once lived in a house whose roof has fallen in. whose指物时通常以以下结构来代替 (3) The classroom whose door is broken will soon be repaired.那个门被打破的教室不久会被修复。 (4) The classroom the door of which is broken will soon be repaired.课堂门，被打破会不久被修复。 (5) Do you like the book whose color is yellow?你喜欢颜色是黄色的书吗? (6) Do you like the book the color of which is yellow?你喜欢的书的颜色，是黄色吗? which指物 在定语从句中做主语，表语，定语或者宾语，做宾语时可省略。 (1) Football is a game which is liked by most boys. 足球是大多数男孩都喜欢的游戏. (2) This is the pen (which) he bought yesterday. 这是他昨天刚买的钢笔.
that指人时
相当于who或者whom；指物时，相当于which。 在定语从句中做主语,表语或者宾语，做宾语时可省略。 (5) The number of the people that/who come to visit the city each year rises one million.数目的人民那个/谁来城市观光每年上升之一个百万 (6) Where is the man that/whom I saw this morning?那个男人在哪里/我看见谁了今天早上?
编辑本段关系副词引导的定语从句
when指时间
在定语从句中做时间状语也可做连接词用 (1) I still remember the day when I first came to the school. (2) The time when we got together finally came.
where指地点
在定语从句中做地点状语 (1) Shanghai is the city where I was born. (2) The house where I lived ten years ago has been pulled down.
why指原因
在定语从句中做原因状语 (1) Please tell me the reason why you missed the plane. (2) I don’t know the reason why he looks unhappy today. 注意：关系副词引导的从句可以由“介词+关系代词”引导的从句替换 (1) The reason why/ for which he refused the invitation is not clear, (2) From the year when/in which he was going to school he began to know what he wanted when he grew up.
1）介词后面的关系词不能省略。 2）that前不能有介词。 3） 某些在从句中充当时间，地点或原因状语的"介词+关系词"结构可以同关系副词when ,where和why 互换。 This is the house in which I lived two years ago. This is the house where I lived two years ago. Do you remember the day on which you joined our club? Do you remember the day when you joined our club? This is the reason why he came late. This is the reason for which he came late. 介词+关系代词引导的定语从句关系代词在定语从句中做介词宾语时 从句常由介词+关系代词引导 当介词放在关系代词前面时，关系代词只能用which/whom即“介词+which/whom"且不能省略。但当介词位于末尾时可用that/which/who/whom.作介词的宾语，且可以省略。例如： (1) The school (that/which) he once studied in is very famous."that/which"可以省略 = The school in which he once studied is very famous."which”不可省略 (2) Tomorrow I will bring here a magazine (that/which) you asked for. = Tomorrow I will bring here a magazine for which you asked. (3) We’ll go to hear the famous singer (whom/that/who) we have often talked about. = We’ll go to hear the famous singer about whom we have often talked. 注意： 1. 含有介词的动词短语一般不拆开使用，如：look for, look after, take care of等 T This is the watch which/that I am looking for. (T＝正确) F This is the watch for which I am looking. (F＝错误) 2. 若介词放在关系代词前，关系代词指人时用whom，不可用who或者that；指物时用which，不能用that；关系代词是所有格时用whose (1) The man with whom you talked is my friend. (T) The man with that you talked is my friend. (F) (2) The plane in which we flew to Canada is very comfortable. (T) The plane in that we flew in to Canada is very comfortable. (F) 3. “介词+关系代词”前可有some, any, none, both, all, neither, most, each, few等代词或者数词 (1) He loved his parents deeply, both of whom are very kind to him. (2) In the basket there are quite many apples, some of which have gone bad. (3) There are forty students in our class in all, most of whom are from big cities.
关系代词
关系代词（一般情况下）that 可用在从句做主语，谓动词的宾语，但是不能做介词的宾语。 which指物，在从句中作主语，谓语或宾语； who在从句中作主语； whom在从句中作宾语； where在从句中修饰表地点的名词，做地点状语； when在从句中通常修饰表时间的名词，做时间状语； why在从句中做原因状语，先行词通常是"reason" 有时why也可用for+which代替。 例：A doctor is a person ‖who looks after people's health. 主语 谓语 先行词 定语从句修饰先行词
自认为以下是重点：
（一）限制性定语从句只能用that的几种情况 1、当先行词是anything, everything, nothing (something 除外), few, all, none, little, some等代词时，或者是由every, any, all, some, no, little, few, much，each等修饰时 (1) Have you taken down everything (that) Mr. Li has said? (2) There seems to be nothing (that) seems impossible for him in the world. (3) All that can be done has been done. (4) There is little (that) I can do for you. 注意1：部分时候that可以省略，如部分例句将that用括号括住。 注意2：当先行词指人时，偶尔也可以用who (4) Any man that/.who has a sense of duty won’t do such a thing. 2、当先行词被序数词修饰 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 This is the best film that I have seen. 4、当形容词被the very, the only，the same,the last ,any,little等修饰时 (1) This is the very good dictionary that I want to buy, (2) After the fire in his house, the old car is the only thing that he owned. 当先行词指人时，偶尔也可以用who (3) 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 (1) Who is the man that is standing there? (2) Which is the T-shirt that fits me most? 6、当先行词既有人，也有动物或者物体时 Can you remember the scientist and his theory that we have learned? 7.当关系代词在定语从句中做表语 The village is no longer the one that it used to be 10 years ago. 8.当在there be句型中，通常情况下用that，不用which （二）关系代词as和which引导的定语从句as和which引导非限制性定语从句，有相同之处也有不同之处。具体情况是： 1、As和which都可以在定语从句中做主语或者宾语，代表前面整个句子。 (1) He married her, as/which was natural. (2) He was honest, as/which we can see. 2、as 引导非限制性定语从句，可放在主句之前，或者主句之后，甚至可以切割一个主句；which引导的非限制性定语从句只能放在主句之后。另外，as有“正如……，正像……”的意思 (1) As is known to all, China is a developing country. (2) He is from the south, as we can see from his accent. (3) John, as you know, is a famous writer. (4) He has been to Paris more than several times, which I don’t believe. 注意：当主句和从句存在逻辑上的因果关系时，常用which。 (5) Tom was always late for school, which made his teacher angry. 3、当先行词受such, the same修饰时，常用as (1) I have never heard such a story as he tells. (2) He is not such a fool as he looks. (3) This is the same book as I lost last week. 注意：当先行词由the same修饰时，偶尔也用that引导定语从句，但是和由as所引导的定语从句意思不同 (4) She wore the same dress that she wore at Mary’s wedding. 她穿着她在MARY婚礼上穿过的一条裙子。 (5) She wore the same dress as her young sister wore. 她穿着和她妹妹所穿的一样的裙子。 注意：定语从句such…as …与结果状语从句such… that…的区别：as在所引导的定语从句中作主语，宾语；that在结果状语从句中不做成分 (6)He has such a good laptop as I want to buy. (7)He has such a good laptop that I want to buy one. (三）以the way为先行词的定语从句通常由in which, that引导，而且通常可以省略。 The way in which/ that/./ he answered the question was surprising. (四) but有时也可以做关系词引导定语从句 There are very few but understand his idea。 ( but= who don’t ) (五) 区分定语从句和同位语从句 1、定语从句修饰先行词，它和先行词是修饰关系； 同位语从句说明先行词的具体内容，是补充说明的关系 (1) The plane that has just taken off is for London. 定语从句 (2) The fact that he has been dead is clear. 同位语从句2、定语从句由关系代词或者关系副词引导，关系词在句中充当成分，有时可以省略；同位语从句主要由that引导，在句中一般不做成分；句子也可以由when, where, how, why, whether, what等词引导，充当成分(1) The news he told me is true. (2) The news that he has just died is true.(3) The problem that we are facing now is how we can collect so much money. 定语 4) The problem how we can collect so much money is difficult to solve. 3、 同位语从句和先行词一般可以用be动词发展成一个完整的句子，而定语从句不可以发展成一个完整的句子，(1) The idea that we could ask the teacher for advice is wonderful. 同位语 (2) The idea was that we could ask the teacher for advice. (3) The fact that the moon moves around the earth is known to all. (4) The fact is that the earth moves around the earth. 〔定语从句〕介词+关系词 1）介词后面的关系副词不能省略。2）that前不能有介词。3）某些在从句中充当时间，地点或原因状语的"介词+关系词"结构可以同关系副词when 和where 互换。例如This is the house in which I lived two years ago. 这是我两年前住过的房子。This is the house where I lived two years ago. Do you remember the day on which you joined our club？ 还记得你加入我们俱乐部的那一天吗？Do you remember the day when you joined our club？
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