定语从句中的特殊用法定语从句是起定语作用的,修饰,说明名词,代词或句子内容的从句,被定语从句修饰的词叫做先行词。
引导定语从句，并在句中担任成分的词叫做关系代词或关系副词。
定语从句是高考常考内容之一，使用时要尤其注意以下十种特殊用法。
一、只用that不用which的情况1、当先行词是all, little, few, much, something,everything, anything, nothing, none等不定代词时。
如：Everything that happened then was like a nightmare.当时发生的一切就像是一场噩梦。
I will tell him all that you told me at the ball.我要把你在舞会上跟我说的话全都告诉他。
2、当先行词被only, any, few, little, no, all, just, very（恰好的,表示强调）等词修饰时。
例如：The only thing that we could do was to wait.我们能做的只是等待。
That’sthe very thing that we can do.那正是我们能做的事。
3、当先行词是序数词、形容词最高级或先行词被序数词或形容词最高级修饰时。
例如：The first place that we visited was the Great Wall.我们参观的第一个地方是长城。
This is the best novel that I have ever read.这是我看过的最好的小说。
4、被修饰词为数词时。
例如：Yesterday I caught two fishes and put them in a basin of water. Now you can see the two that are still alive.昨天我捉到了两条鱼，把它们放在一盆水里。
你可以看到那两条鱼还活着呢。
5、主句是There be结构，修饰其主语的定语从句宜用that作关系代词修饰物。
例句：There’sstill a room that is free.还有一个空房间。
6、先行词中同时包括人和物时。
例如：We talked about the people and the villages that we remembered.我们谈论了我们记得的人和村子。
He asked about the factories and workers that he had visited.他问起他去过的这几家工厂和工人的情况。
7、当主句中有who, which时，而定语从句中也要用到who或which时，为了避免who…who,which…which等重叠，定语从句要用that引导。
例如：Who is the man that is standing by the door?站在门边的那个男人是谁？Which of the two cows that you keep produces more milk?你养的那两头奶牛中哪一个产奶多？8、人或物在定语从句中表语时，用that引导定语从句，而that通常也可以省略。
例如：He is no longer the man that he was.他不再是过去的他。
二、修饰物时只用which不用that的情况1、引导非限制性定语从句时。
例如：Bamboo is hollow, which makes it light.竹子是空心的，这使得他很轻。
2、当关系词前有介词时。
例如：This is the room in which Chairman Mao once lived.这就是毛主席曾经住过的地方。
3、在一个句子中有两个定语从句，其中一个定语从句的关系代词用了that,另一个宜用which。
例如：Let me show you the novel that I borrowed from the library which was newly open to us.我来给你看我从新开的图书馆里借来的那本小说。
4、当关系代词后面有插入语时。
例如：Here is the English grammar which, as I have told you, will help improve your English.这就是我跟你说过的会有助于你学好英语的那本英语语法书。
5、先行词为that时。
例如：The clock is that which can tell us the time.钟是报时的装置。
1三、修饰人时只用who不用that的情况1、先行词为one, ones, anyone, those指代人时。
如：The person I want to learn from is one who studieshard and works well.我最羡慕的是学习勤奋，工作出色的人。
2、在There be结构中，修饰主语的定语从句宜用who关系代词指代人。
例如：There’sa gentleman who wants to see you.有位先生想见你。
3、当先行词有较长的后置定语时。
例如：I met a foreigner in the park yesterday afternoonwho could speak Chinese very well.昨天下午我在公园里遇到一位中文讲得非常好的外国人。
4、一个句子中带有两个定语从句，其中一个定语从句的关系代词是that,另一个宜用who以避免重复。
The student that was praised atyesterday’smeeting is the monitor who is verymodest and works very hard.受到校长表扬的学生是位谦虚好学的班长。
注意：当关系代词前面有介词时，只能用whom。
例如：The person to whom this letter was addressed died three years ago.这封信的收信人三年前就去世了。
四、way在定语从句作先行词的用法当先行词为way时，定语从句的引导词可用in which, that或省略引导词。
例如：Idon’tlike the way（that /in which）he looks at me.我不喜欢他那种样子看着我。
五、在定语从句中作状语的关系副词when, where, why的用法1、先行词表示时间时，定语从句中的谓语动词如果是不及物动词，用关系副词2when或介词+ which;如果是及物动词，用which或that都行。
例如：I still remember the days when（=on which）we lived together.我仍然记得我们在一起的时光。
2、先行词表示地点时，如果定语从句中谓语动词是不及物动词，用关系副词where或介词+which;如果是及物动词时，用which或that都可以。
例如：This is the small village where (=in which) Chairman Mao ever lived.这就是毛主席曾经居住过的小村庄。
3、表示原因时，why前的先行词是表示原因的名词reason。
例如：Can you tell me the reason why (=for which) youdidn’tfinish y our homework?你能告诉我你没有完成作业的原因吗？六、whose引导的定语从句Whose引导定语从句时，其先行词可以指人，也可以指物，当先行词指物时，可以用the+名词+of which的结构。
例如：He studies in a school whose buildings(=the buildings of which) are built on top of a hill.他就读的学校其房子都建在山顶上。
七、as作关系代词引导的定语从句1、引导限制性定语从句。
在主句中常有the same, so或such与as相呼应, as在定语从句中可作主语、宾语、主语补足语等。
as引出的定语从句带有比较意义，从句常常只写出比较部分，但as本身不可省略。
例如：He used such expressions as he could find in the texts.他使用在课文中可以找到的那些词语。
They stayed for the night in the same room as they had once rented.他们在他们3曾租用过的同一房间过夜。
注意：在thesam e…后也可用that引导定语从句，但含义有所不同。
that引出的从句，指的是与先行词同一的事物，而as引导的从句指的是与先行词同类的事物。
例如：This is the same bag as I lost yesterday.这个包和我昨天丢失的包的样子是同样的。
This is the same bag that I lost yesterday.这就是我昨天丢失的那个包。
2、引导非限制性定语从句。
带主句的全部或部分内容。
常译为“正如-------”“就像------”等常用于肯定句中，定语从句可以置于主句句首、句中或句末。
as 后常接expect, know, report, say, see等动词的主、被动语态。
例如：As is known to everybody, the moon travels round the earth once every month.正如大家所知道的那样，月球每月绕着地球转一圈。
Hewasn’tunconscious, as could be judged from his eyes.他并未失去知觉，这从他的眼神可以看出来。
注意：as, which引导非限制性定语从句的区别：1）、都可以代整个主句，相当于and this或and that.2）、as可放在句首，而which不能。
3）、as代表前面的整个主句并在从句中作主语时，从句中的谓语必须是系动词；如果为行为动词，则从句中的关系代词只能用which.例如：It rained hard yesterday, which prevented me from going to the park.昨天下大雨，这使得我不能去公园。
4）as常用于肯定句中译为“正如”，which常用于否定句中翻译成“这点”He failed in the exam again, as we expected./ which was unexpected.4As的固定搭配：as has been said before如前所述as often happens正像经常发生的那样As is well known众所周知as we know ,as is imagined, as we can see八、of短语作为定语从句的先行词的情况one of the +复数名词这一结构后面的定语从句中的谓语动词，通常用复数形式，与定语从句所靠近的那个复数名词在数上保持一致。