语法专题（一）定语从句考点一：关系代词的用法1．关系代词的作用和分类(1)关系代词的作用有三个：①连接作用：关系代词引导从句，把它和主句连接起来；②替代作用：关系代词在从句中替代它前面的先行词；③成分作用：关系代词在从句中充当主语、宾语、表语、定语成分2)关系代词的用法分类关系代词的用法分类有三点依据：①根据所引导的从句的限制性和非限制性；②根据所替代的先行词是指人还是指物；③根据它在从句中所充当的成分——主语、宾语、表语或定语2．易混关系代词辨析(1)关系代词that和which先行词是物时，关系代词that，which一般可以通用，但也有区别1)只能用that的情况①先行词为指物的不定代词(all, nothing, the one, much等)或被不定代词修饰时，如：You can take any seat that is free.Tell us all that you know.②先行词是序数词或被序数词修饰时，如：That is the first composition that I've written in English.③先行词是形容词最高级或被形容词最高级修饰时，如：This is the best way that has been used against pollution.④当人和物同为先行词时，如：Everyone wants to see the spaceship and the spaceman that made the flight around the earth.⑤关系代词在从句中作表语时，如：He is no longer the man (that) he used to be.⑥先行词被the only，the very修饰时，如：That is the very pen (that) I am looking for.⑦当先行词是which时，如：Which of the two cows that you keep produces more milk?⑧先行词为the way/the time/the moment/the first time/the last time等名词时，如：I don't like the way(that)he talks.This is the third time(that)he has been late this week.注意：此时that为关系副词，若先行词没有被the first/the last修饰时，用that和when均可，如：The time (that)/(when) I saw you was 8：00.(2)关系代词as和whichas既可指人又可指物，主要用于as…；as…as；the same…as…；such…as…等结构中，在从句中作主语、宾语或表语。
引导的从句可位于句中、句首、句末如：As is reported in the newspaper，talks between the two countries are making progress.Mary was late for school，as is often the case.as引导非限制性定语从句，修饰整个句子，而which不仅可修饰整个句子还可以修饰单个名词如：The meeting，which was held in the park，was a success.The meeting was a success，as was expected.(3)who和that先行词是人时，关系代词可用who(m)，that引导定语从句，但下列情况一般用who，而不用that①先行词是one，ones，anyone或anybody，those时，如：Anyone who breaks the law should be punished.②一个句子中带有两个定语从句，其中一个的关系词是that时，如：The student that won the first prize is the monitor who speaks English best in our class.③在there be句型中和非限制性句型中，如：There is a person who wants to see you.I met an old classmate yesterday, who is now a manager of a big company.(4)who，whom和whosewho指人，在定语从句中作主语或宾语，whom指人，在定语从句中作宾语。
作宾语时who和whom一般可通用，但直接放在介词之后时，一般只用whom，不可用who如：Take your problem to the person who you think can help you.She is the girl (who/whom) I will go to Shanghai with.＝She is the girl with whom I will go to Shanghai.whose既可指人，也可指物，在从句中作定语如：George Orwell，whose real name was Eric Arthur，wrote many political novels.The librarian refused to accept the book，whose cover was gone when it was returned.3．关系词的省略①作宾语的关系代词可以省略，但前面不能有介词如：This is the man(who/whom/that) we have talked about.②口语中，关系副词可以省略(尤其是先行词为time，way，reason等时)。
如：This is the reason (why)I did it.I don't know the time (that) he arrived.4．限制性和非限制性定语从句①限制性定语从句起修饰限制的作用，是主句不可缺少的一部分，与先行词无逗号隔开，翻泽成中文常译成前置定语如：Those who want to go，sign their names on the paper.那些想去的人把他们的名字签在纸上5．定语从句中的主谓一致①关系词在定语从句中作主语时，从句的谓语动词要与先行词保持一致如：I，who am your friend，will leave for Beijing tomorrow.which和as指代一个句子时，从句谓语动词用单数如：Mary is often late for class，which makes our teacher very unhappy.6．“介词/介词短语＋which/whom”中介词的选择关系代词前面的介词使用是根据与名词前面的动词搭配关系和介词的搭配关系及句子结构上的需要而定的如：We'll never forget the day on which we went camping.(on the day)The woman to whom we spoke is from the USA. (speak to sb.)His glasses，without which he was(＝who was not)like a blind man, fell to the ground and broke.(由句意决定)考点二：关系副词的用法1．当先行词在定语从句中作状语时，要用关系副词。
其中when＝表示时间的介词(如：in，at，during等)＋which；where＝表示地点的介词(如：in，at，on，under等)＋which；why＝for＋which如：I still remember the day when I first came to Beijing. (when＝on which)Can you tell me the office where he works? (where＝in which)Do you know the reason why he is absent? (why＝for which)2．高考对关系副词where的考查高考试题中对于where的考查趋于复杂，从先行词由“明显的地点”转为“地点的模糊化”事实上，对于where这个词，考生不能只理解为表示地点当先行词表示某人/物的处境，或某事所发展的阶段，或表达某事的某个方面时都可用where这个关系副词如：The accident had reached to a point where both their parents are to be called in.事情发展到如此程度，不得不请双方家长来一趟了。
试比较下面的句子：①Do you still remember the days that/which we spent in Qingdao?你还记得我们一起在青岛度过的日子吗？②Do you still remember the days when we spent the summer holidays in Qingdao?你还记得我们在青岛过暑假的日子吗？在句①中，定语从句中缺宾语，因此须用关系代词that/which来引导从句，而在句②中，定语从句中不缺主语，也不缺宾语，因此须用关系副词when来引导从句2．定语从句与其他句式的比较It is such a heavy box that he can't lift it.(状语从句)It is such a heavy box as he can't lift.(定语从句)Is this factory the one in which/where we lived three years ago？(定语从句)Is this factory where we lived three years ago？(表语从句)As is known to the world, Mark Twain is a great American writer.(定语从句)It is known to the world that Mark Twain is a great American writer.(主语从句)That Mark Twain is a great American writer is known to the world.(主语从句)We don't understand the problem why this is the best choice.(同位语从句)The reason that he gave was not right.(定语从句)She did all she could to help him.(定语从句)She is not the girl she used to be.(定语从句)She did what she could to help him.(宾语从句)She is not what she used to be.(表语从句)由以上例句可以看出，分清定语从句与其他复合句的关键是要掌握先行词及其后的关系词，要看其是否在从句中作成分，是否有意义。