高中定语从句精讲老师叮咛：李辉老师说，学任何东西先要把一些概念说清楚——正名的过程“名不正则言不顺”做任何一门学问，要知道这里头的概念说的是什么意思——这就是所谓的“正名”。
无论学习什么，必须先搞定定义，明白我们要学习的是什么。
下面有关定语从句的内容非常重要，希望你可以学会。
经过了全网首席高考英语名师李辉老师团队高度认真地整理校对、无错、可信！可供全国各省高中生打印、背诵！1．什么是定语从句（attributive clause）?定语从句从字面上看就是指在句中充当定语的句子。
著名语法学家薄冰解释为，定语从句在句中作定语用，修饰句中的某一名词或代词。
定语从句所修饰的词叫先行词。
一般说来，定语从句紧跟在所修饰的先行词之后。
Eg：I don’t like the book（先行词）that I bought yesterday（定语从句）.2．限制性定语从句和非限制性定语从句：根据定语从句和先行词的语义关系把定语从句分为限制性定语从句和非限制性定语从句。
限制性定语从句与主句关系非常密切，通常没有逗号隔开。
限制性定语从句在句中不可缺少，否则主句的意义将不完整。
非限制性定语从句与主句关系较为松散，它只是对先行词的附加说明，即使省去也不影响主句的意义。
例如：Eg：1）This is the best film that I have ever seen. （限制性定语从句）2）Last night I saw a very good film, which was about robots. ( 非限制性定语从句）3．定语从句的关系词：定语从句的关系词按功能分为两类，一类为关系代词，在从句中充当主语和宾语；一类是关系副词，在从句中充当状语。
详见以下思维导图：↗which : 指物，在从句中可充当主语和宾语↗that : 既可指人也可指物，成分同上↗关系代词→who : 主格，指人，在从句中可充当主语↘whom : 宾格，指人，在从句中可充当宾语定语从句关系词↘whose : 所有格，既可指人也可指物，充当从句中定语，指人有时也用of whom, 指物时也可用of which↗when : 在从句中充当时间状语↘关系副词↘where : 在从句中充当地点状语4.选择关系词的诀窍：通常来说，选择关系词的诀窍是：1）判断是否为定语从句A．定语从句一定要有先行词，否则不是定语从句，例如，Put the book where it is. 在此where引导的是地点状语从句，因为它没有指定地点的先行词，所以不是定语从句。
但很多同学会用in which来代替where, 是错把此句当定语从句看。
试比较：Put the book to the place where it belongs.（此句where引导的定语从句修饰先行词the place）B．定语从句为主从复合句，切莫把并列句当定语从句而使用关系词。
例如：Many students got high marks this time, but only few of______are boys.a. whob. whomc. themd. which许多学生错选择答案b. whom。
为什么呢？错误在于此句有并列连词but，因此应选择答案c. them。
试比较：Many students got high marks this time, only few of whom are boys.2）找出从句中缺少什么成分，再判断是指人还是指物，或指时间还是地点，据此以选择关系词，如：A．This is the place where I once worked for five years.B．This is the place that I visited a few days ago.A句用where是因为结合先行词来看从句缺少地点状语，而B句用that是因为结合先行词来看从句缺少指物的宾语。
3）有时也可采取这样的办法，即把从句和先行词连接起来，如果可连接且不缺任何成分，则选关系代词；如果不可直接连接而需补充其它词，则用关系副词，如：A．I will never forget the days when we played and studied together.B．I will never forget the days that we spent together.A句用when，是因为当我们把从句和先行词the days连接时，必须加上介词on方能连接。
例如：We played and studied together on the days.这里的the day前面就要用介词on。
B句用that，是因为从句和先行词the days可以直接连接，而不需补充任何词。
例如：We spent the days together.5.特殊关系词引导的定语从句1）关系代词as关系代词as通常用在如下一些句型中：A．As is known to all/As you know , paper was first made in China. (as在从句中作宾语，指代整个主句的含义，有“正如---”之意）比较：It is known to all/You know that paper was first made in China.注意：which也有类似用法，然而which引导的定语从句不能放在句首，而as引导的定语从句可以放在句首，也可在句末。
例如：Dorothy was always speaking highly of her role in the play, ________, of course , made the others unhappy.a．who b．which c．this d．what （本题为2000年高考题，选b）B．I have the same trouble as you have.不过，当先行词被same修饰，且指“同一物品”时要用that。
例如：She is wearing the same dress that she wore yesterday.C．He is such a kind person as is always ready to help others.2）关系副词why关系副词why（可由for which替代）通常跟在先行词the reason后引导定语从句，表示“---的原因”。
例如：The reason why he was late is that he helped an old man on his way to school.注意比较：The reason that he gave to the teacher is unreasonable.二者的区别。
6．指物时特定条件下which和that的选择：有些场合我们宜用关系代词that，这些场合有：1）先行词由序数词和形容词最高级修饰时，例如：This is the first novel that I have ever read.This is the most exciting film that I have ever seen.2）先行词为all, everything, nothing, anything, little等不定代词时，例如：All that I need is a good rest. （that在此为从句宾语，可省略）注意比较：What I need is a good rest.不过：something后关系代词用that和which均可。
3）当先行词有the only, the last, the very修饰时关系代词用that，例如：This is the only thing that I want to do now.This is the very book that interests me.This is the last thing that I will do.4）当先行词既有人又有物时关系代词用that，例如：I like the books and the authors that our teacher introduced to us this morning.5）当先行词为疑问代词who，或在who疑问句中时，关系代词用that，例如：Who that has common sense will do such a thing?Who is the girl that got the first prize in the competition?6）当关系代词在定语从句中作表语时用that。
例如：This is no longer the place that it used to be。
He is not the man that he was.7) 定语从句内容为解释名词的性质、概念时，需用that。
如：A plane is a machine that can fly.有些场合宜用关系代词which，例如：1）限制性定语从句中指物时关系代词用which，例如：They have gone to Beijing, which is the capital city of China.2）作介词的宾语并紧跟在其后使用which，The ladder on which I was standing began to slip.注意比较：The ladder which/that I was standing on began to slip.还要注意：当介词为与动词构成的固定短语时介词不可放在关系代词前，例如：This is the book that I have been looking for.不可以说成，This is the book for which I have been looking.3）作先作词的集体名词着眼于集体的整体，关系代词用which；若是指集体中的各个成员，则用who，例如：A.The class, which is winning, is Class One, Grade Two.B.The class, who are all trying their best to do good deeds today, is in the charge of Mr.Zheng.7．避免从句中出现与关系代词意义重复的词：要对学生强调关系词本身在从句中充当一定的成分，而避免出现重复词。
常见错误：1）The book which you want to buy it is sold out. （which指代the book，it为重复词）2）The house where he lives in is very large.（where指代in the house, in为重复词）8．如何区分定语从句与同位语从句：许多学生容易混淆that引导的定语从句和that引导的同位语从句。