高中英语定语从句精讲及练习英语从句可分三类：一、形容词性从句（定语从句）二、状语从句三、副词性从句（状语从句）定语从句定语从句：修饰一个名词或代词的从句称为定语从句，一般紧跟在它所修饰的先行词后面。
关系词：引导定语从句的关联词成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；关系副词有where, when, why等。
关系词常有3个作用：1，引导定语从句。
2，代替先行词。
3，在定语从句中担当一个成分。
如何确定关系词？一看先行词；二看先行词在从句中充当的成分。
一、关系代词引导的定语从句1.who指人，在从句中做主语(1) The boys who are playing football are from Class One.(2) Yesterday I helped an old man who lost his way.2. whom指人，在定语从句中充当宾语，常可省略。
(1) Mr. Liu is the person (whom) you talked about on the bus.(2) Mr. Ling is just the boy whom I want to see.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。
(3)The man who/whom you met just now is my friend.1.The man ______________is talking to me is a friend of my father’s.2.The school __________________is famous here has a long history.3.I live in the house _________windows face south.4.He is the boy________we are waiting for.3. which指物，在定语从句中做主语或者宾语，做宾语时可省略(1) Football is a game which is liked by most boys.(2) This is the pen (which) he bought yesterday.4. that指人时，相当于who 或者whom；指物时，相当于which。
在宾语从句中做主语或者宾语，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.(6) Where is the man that/whom I saw this morning?5. 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.(2) I once lived in a house whose roof has fallen in.whose指物时，常用以下结构来代替(3) The classroom whose door is broken will soon be repaired.(4) The classroom the door of which is broken will soon be repaired.(5) Do you like the book whose cover is yellow?(6) Do you like the book the color of which is yellow?二.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(1) The school (that/which) he once studied in is very famous.(2) The school in which he once studied is very famous.(3) Tomorrow I will bring here a magazine (that/which) you asked for.(4) Tomorrow I will bring here a magazine for which you asked.(5) We'll go to hear the famous singer (whom/that/who) we have often talked about.(6) 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(1) This is the watch which/that I am looking for. (T)(2) This is the watch for which I am looking. (F)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)(2) The man who/that you talked with is my friend. (F)(3) The plane in which we flew to Canada is very comfortable. (T)(4) 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.三．关系副词引导的定语从句1. when指时间，在定语从句中做时间状语(1) I still remember the day when I first came to the school.(2) The time when we got together finally came.2. 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.3. 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.(3) Great changes have taken place in the city in which/where I was born.三．限制性定语从句和非限制性定语从句区别：一、在句中作用不同限制性定语从句对被修饰的先行词有限定制约作用,使该词的含义更具体,更明确。
限制性定语从句不能被省略,否则句意就不完整。
非限制性定语从句对先行词作一些附加说明,不起限定制约作用。
如果将非限制性定语从句省去,主句的意义仍然完整。
二、外在形式：逗号隔开三、先行词内容有所不同：大多数限制性和非限制性定语从句的先行词往往为某一个词或短语,而特殊情况下非限制性定语从句的先行词也可为整个主句,此时非限制性定语从句常由which 引导。
A five-year-old boy can speak two foreign languages, which surprises all the people present.四、关系词的使用1、that 不可用于引导非限制性定语从句2、关系代词whom 在限制性定语从句中作宾语时可用who 代替whom ,但whom 在非限制性定语从句中作宾语时不可用who 来代替。
3、关系代词在限制性定语从句中作宾语时可以省去,非限制性定语从句的所有关系词均不可省。
限制性定语从句举例：(1) The teacher told me that Tom was the only person that I could depend on.(2) China is a country which has a long history.非限制性定语从句举例：(1) His mother, who loves him very much, is strict with him.(2) China, which was founded in 1949, is becoming more and more powerful.要注意区分以下几个句子的不同(1) His brother who is now a doctor always encourages him to go to college.他那当医生的哥哥常鼓励他要考上大学。
（他还有其他的哥哥）(2) His brother, who is now a doctor, always encourages him to go to college.他的哥哥是当医生的，常鼓励他要考上大学。