高中英语定语从句详解定语从句主要用于修饰句子中的名词、代词或上文提到的一件事（句子）。
而定语从句的位置常常是紧跟在被修饰的名词、代词或句子的后面。
在被修饰的名词、代词（先行词）与定语从句之间往往有一个关系词将其前后两部分联系成一个整体。
关系词与后面的句子合称定语从句。
1）three signs that indicate a person is suffering from a heart attack三种意味着一个人患心脏病的迹象在这个带有定语从句的短语中：signs是：被修饰的名词；that是：关系词；that indicate a person is suffering from a heart attack是定语从句2）those who drink a lot 那些大量饮酒的人在这个带有定语从句的短语中：those是：被修饰的代词；who是：关系词;who drink a lot是：定语从句。
3）Do you know the name of that girl whose brother is your roommate ?你知道她的哥哥与你同寝室的那位女孩的名字吗？通过上面的演示,我们可以归纳出：（1）定语从句在英语中放在被修饰的词后，翻译成汉语时置于被修饰的词之前，且有汉字“的”（2）定语从句在句子中的位置、结构如下：被修饰的名词/ 代词+ 关系词+ 句子(其中，"被修饰的名词/代词"在语法叫作"先行词".) 要点提示：1）先行词=关系词。
所以先行词在从句中不在出现。
先行词的意义以及它在从句中的语法功能（句子成分）决定关系词的选择。
定语从句中的关系词只有两类：关系代词和关系副词；所有关系词不但都有具体的意义而且都在从句中担任一定的成分。
1）关系代词：who , whom , whose , which , that 等。
who用于代替"表示人的意义"的先行词，并且在从句中充当主语，也可充当宾语。
但不能放在介词之后。
介词后的宾语用whomwhose 用于代替"表示人或物意义"的先行词，用在从句中时，后要跟一个名词，与那个名词合起来相当于一个关系词，在从句中担当主语或宾语。
Whose常表达"先行词的"之意which 用于代替"表示事物意义"的先行词，在从句中作主语、宾语。
that 既用于代替"表示人的意义"的先行词，也用于代替"表示事物意义"的先行词；在从句中既可以作主语，也可以作谓语动词的宾语，但是不能跟介词后作介词的宾语，介词后用which。
在一定范围内，that = who / whom / which 。
要点提示：虽然that即可指人，也可指代物，习惯上指代人时，常用who。
总结：（1）怎么判断定语从句（2）怎么选择关系词：当先行词指.....时如：填空，翻译1) I have no idea about the man wrote the article .2) The little boy is singing there can recite quiet a number of Chinese poems .3 )I know the girl you talked to just now4 )That was a fault could not be forgiven .5)I've got a novel you may like to read .6 )This is the book from I know the famous person.7)Who is the girl you talked to just now?8) This is the very book you are looked for yesterday.9) The books which sell well are written by him.10) The book which sells well is written by him.11)The world we live in is made of matter.12)The world in we live is made of matter.要点提示：（1）关系代词在定语从句中作宾语时可以省略。
避免重复，指人时，主句有who，从句用that（2）That 和which 指代物时的区别先行词本身是all , everything , something , nothing , anything等不定代词时，例如：All that I have is money.There must be something that happened to you .你一定出了什么事。
They had nothing that could cure of his disease .他们没有一点能治愈他疾病的东西了。
-- 先行词已有序数词或形容词的最高级或the last, the only等作定语时，例如：This is the most impressive TV that has never been put on show before . 这是以前从未上演过的最有感染力的电视剧。
That is the only way that leads to your success .那是通向你成功的唯一之路。
We have to consider the first thing that we need to do.我们必须要考虑我们需要做的第一件事。
-- 当先行词表示事物意义，并且在从句中作介词的宾语，那么就只能用whichIt is the second thing about which I become crazy.(3)定语从句中，谓语动词的单复数取决于先行词的单复数。
特例：1 She is one of the students who have been abroad.2 She is the only one of the students who has been abroad.2)关系副词：when = 在什么时候，where = 在什么地方，why = 为什么原因，在英文中用哪个具体的介词，得依具体汉语意思而定了关系代词在从句中作主语、宾语或表语，关系副词在从句中作状语（不缺主语，宾语，表语）when 代替表示时间的名词，在从句中充当状语例如：1)People will always remember the time Hongkong and Macao returned to our motherland .2)We don't know the exact time the English Evening will be held .3)I still remember the days we spent together.where 代替表示地点的名词，在从句中充当状语。
例如：1)The place we're to have the Speech Contest has not been decided yet. 2）He is living in a newly-built house there used to be a pond .3）He has found the school his mother told him.why 代替表示原因的名词，在从句中充当状语。
例如：1)He didn't tell her the reason he was so happy .2)They explained the reason to us they had misunderstood us before .3)The reason he explained is not so acceptable .当名词时way时，关系词可以用that，in which或省略关系词He can’t understand the way the teacher told him.He can’t understand the way the teacher solve problem。
He can’t find a way really works.关系副词=介词+关系代词，而这种结构中较难解决的问题是介词的选择问题，因为这个问题的解决取决于多种因素：A）动词与介词的搭配B）名词与介词的搭配C）形容词与介词的搭配，等等。
总之，要依从句的具体需要而定。
例如：A）动词与介词的搭配He has found a good job for which he is qualified .（qualify + 名词+ for "使…具有…资格" ）他找到了一份他能胜任的工作。
The man to whom you talked just now will chair the meeting tomorrow . （talk to + 名词"与某人谈话" ）你刚才与他谈话的那个人明天主持那个会议。
B）名词与介词的搭配They are still living in the little house in which (= )they've been living for 15 years . （in the house "在屋子里" ）他们现在还住在他们已住了15年的那个小房子里。
He went through a hard time during which (=) he lost many times.C）形容词与介词的搭配The secretary with whom the boss is not happy will be fired for her inefficiency . (happy with "对…表示满意")老板对其不满意的那个秘书将由于她没有工作效率而被解雇。
I've found the job for which I've been eager for a long time.（eager for "渴望得到…" ）我已找到了我渴望已久的那份工作。
He is a learned man with whom we are familiar .(familiar with 熟悉…)他是一位我们熟悉的有学识的人。