一、基本概念：
在复合句中修饰某一名词或代词的从句叫做定语从句，也叫形容词性从句。被修饰的名词或者代词叫做先行词。定语从句通常出现在先行词之后，由关系代词或者关系副词引出。定语从句分为两类：限定性定语从句和非限定性定语从句。限定性定语从句与主句关系密切，对先行词有修饰限定作用，如果去掉主句的意思就不完整；而非限定性定语从句只是对先行词做附加的说明，常与主句间用逗号隔开。
定语从句的引导词分为：关系代词和关系副词。
二、引导词的具体用法：1.如果定语从句的先行词指人，那么常用关系代词who作主语，用whom作宾语(此时可省略)
eg. I discussed it with my brother, who is a lawyer.
Do you know the woman (whom)we met at the gate?
2.如果定语从句的先行词指物，那么关系代词that和which常常可以互换，但是在以下的情况中从句的引导词只能用that：1)当先行词是不定代词all，much, any, few, every, ---thing, ---body, ---one, none, the one 等时；
Do you have anything that you want to say for yourself?
You should hand in all that you have!
2)当先行词被the only, the very, the same, any, few, little, no, all等修饰时；
This is the very person that I am looking for.
The only thing that we can do is to give you some money.
3)当先行词是形容词最高级或者被形容词最高级修饰限制时；
This is the best that has been used against pollution.
This is the most interesting film that I have ever seen.
4)当先行词是序数词或者被序数词修饰限制时；
The train is the last that will go to Beijing.
What is the fist American film that you have seen?
5)当先行词既有人又有物时；
Do you know the persons and things that they are talking about?
6)当主句是以wh-开头的特殊疑问词开头的特殊疑问句时，定语从句的引导词用that；
Which is the bike that you lost?
Who is the boy that won the gold medal?
7）当先行词在主句中作表语，且关系代词在从句中的句子成分也是表语时
Shanghai is no longer the city that it used to be.
3.在定语从句中必须用which的情况:
1).在非限定性定语从句中，只能用which，此时既可以表示先行词是物的情况，又可以用which来指代上文中整个句子的内容。
Hellen was much kinder to her youngest son than to the others, of course, which made the others envy him.
2). 当引导词是介词 关系代词时，若先行词指物，只能用which。
※先行词是the way时，引导词用that, in which, 也可省略。
eg. I don’t like the way (that/in which) you laugh at her.
4.Whose的用法当先行词与引导词后的名词间存在所属关系时，引导词用whose。并且whose 名词=the 名词 of which（先行词指物时）/whom（先行词指人时）
eg. Do not get close to the house whose roof is red
=Do not get close to the house the roof of which is red.
5. as 引导的定语从句1）、as 可以在定语从句中做主语或宾语，代表前面整个句子。
eg. He is honest, as we can see.
2）、as 引导的非限制性定语从句可以放在主句之前、主句之后，甚至还可以分割主句。 另外，as 常 常有“正如、正像”的含义。
eg. As is known to all, China is a developing country.
He is from the south, as we can know from his accent.
John, as you know, is a famous writer.
3)、当先行词受such, the same 修饰时，关系词常用as。
eg. I’ve never heard such stories as he told.
This is the same dictionary as I lost last week.
※.当先行词受the same 修饰时，偶尔也用 that引导定语从句，但与as引导的定语从句意思有区别。
eg. She wore the same dress that she wore at Mary's wedding.
She wore the same dress as her younger sister wore.
6.当先行词是表示时间、地点、原因时，要注意分析从句中到底缺少什么句子成分，若缺少主语，宾语或是表语则用which或that都可以。但是如果不缺少这样的句子成分，则根据情况选择相应的关系副词。
eg. Do you still remember the time that/ which we spent together in our childhood?
Do you still remember the time when we worked together in the factory?
1).when引导的定语从句的先行词往往是表示时间的名词，如time, day, week, month, year等，when在从句中作时间状语。
eg. Sunday is a day when people don’t have to go to work.
※先行词是occasion且从句中缺少状语时，从句的引导词用when。
2).Where引导的定语从句的先行词往往是表示地点的名词，Where在从句中作地点状语。
eg. She is teaching at the university where her mother once studied.
※situation, case, stage, point时定语从句缺少的句子成分是状语时，引导词常用where。
I can think of many cases where students obviously know a lot of English words and expressions but couldn’t write a good essay.
3).Why引导的定语从句的先行词往往是表示原因的名词，Why在从句中作原因状语。
Do you know the reason why he changed his mind?
三．介词 关系代词 引导定语从句在这一结构中，关系代词只能用which和whom，当先行词指物时，关系代词用which；当先行词指人时，关系代词用whom。
产生这种结构的原因：1关系副词when，where，Why可以用这一结构替换；2有些动词短语中的介词可以提前到关系代词前。
介词的选用：根据从句中的动词的固定搭配而确定；
关系代词的确定：根据先行词指人还是指物而确定。
1. This is the house in which /where we lived 10 years ago.
2. Class 10 is the class to which I belong
3. He paid the boy 10 dollars for washing 10 windows, most of which hadn’t been cleaned for at least a year.
4. In the dark street, there wasn’t a single person to whom she could turn for help.
5. The gentleman about whom you are talking is in the next door.
四、定语从句中谓语动词的人称和数
定语从句中谓语动词的人称和数根据先行词确定。
one of 可数名词复数 关系代词 复数谓语
the only one of 可数名词复数 关系代词 单数数谓语
eg. 1．The Great Wall is one of the world-famous buildings that/which draw lots of visitors.
2. He is the only one of students who knows the answer to the question.
五、定语从句与同位语从句的区别同位语从句与定语从句从形式上看好像没什么区别，实际上从含义和功能上看，还是比较易区分的。同位语从句的先行词一般为fact, idea, news, thought, reply, report, problem等抽象名词。关联词that在同位语从句中仅仅起连接作用，不作任何成分，但又不可省略。定语从句的关联词（关系代词和关系副词）在从句中是要充当句子成分的且有实际含义。
eg.The suggestion that we should practise speaking English every day came from our monitor. The suggestion that our monitor put forward at the meeting is very valuable.
六、定语从句与强调句型的区别 强调句型一般总是使用It is…that…这个句式，将被强调的成分（主语、宾语或状语）放在句式里。这个关联词that没有任何实际意义，仅仅起连接作用。定语从句一般不用It is开头，而且定语从句的关联词that在从句中担当句子成分。eg. It is Professor Johnson who is to visit China Agricultural University next week.
This is Professor Johnson, who is to visit China Agricultural University next week.
七、定语从句解题步骤：1．意识到定语从句的存在。找到先行词（名词或者代词）。
2．找到从句。从句标志引导词----句子从引导词开始-----保证是句子（句子成分完整）。
3．划分从句的句子成分。确定从句中缺少的句子成分（选择引导词的词类）。
缺少主语宾语表语----------选择关系代词
不缺少主宾表----------------选择关系副词
4选具体的某个引导词。根据以上确定的结果, 选择合适的引导词。
,
