定语从句定语从句（Attributive Clauses）在句中做定语，修饰一个名词或代词，被修饰的名词,词组或代词即先行词。
定语从句通常出现在先行词之后，由关系词（关系代词或关系副词）引出。
关系代词有：who, whom, whose, that, which等。
2.whose+名词=the+名词+of which/ of whom1.宜用that引导的定语从句(1) 如果先行词是all, much, anything, something, nothing, everything, little, none等不定代词，关系代词一般只用that，不用which。
例如：All the people that are present burst into tears.(2) 先行词有两个，既有人也有物，要用that。
We were talking about the persons and things that we remembered in our school.(3) 如果先行词被形容词最高级以及first, last, any, only, few, mush, no, some, very 等词修饰，关系代词常用that, 不用which, who，或whom。
例如：This is the most impressive TV theater 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 starts our work .我们必须要考虑启动我们工作的第一件事。
2. 宜用which引导的定语从句当定语从句的介词提前时，要用which。
The house in which they lived last yearhas been rebuilt.引导非限制性定语从句时，要用which。
He bought a railway ticket for the woman,which helped her a lot.as, which 非限定性定语从句由as, which 引导的非限定性定语从句，as和which可代整个主句，相当于and this 或and that。
As一般放在句首，which在句中。
As we know, smoking is harmful to one's health.The sun heats the earth, which is very important to us.Alice received an invitation from her boss, ___came as a surprise.A. itB. thatC. whichD. heIt rained hard yesterday, ____ prevented me from going to the park..A. thatB. whichC. asD. itas 和which在引导非限制性定语从句时，这两个关系代词都指主句所表达的整个意思，且在定语从句中都可以作主语和宾语。
但不同之处主要有两点：(1) as 引导非限制性定语从句，可放在主句之前，或者主句之后，甚至可以切割一个主句；which引导的非限制性定语从句只能放在主句之后。
另外，as有“正如……，正像……”的意思(2）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；若为行为动词，则从句中的关系代词只能用which。
(3)当先行词受such, the same修饰时，常用asI have never heard such a story as he tells.He is not such a fool as he looks.This is the same book as I lost last week.当先行词由the same修饰时，偶尔也用that引导定语从句，但是和由as所引导的定语从句意思不同。
She wore the same dress that she wore at Mary’s wedding.她穿着她在MARY婚礼上穿过的一条裙子。
She wore the same dress as her young sister wore.她穿着和她妹妹所穿的一样的裙子。
判断关系代词与关系副词方法一：用关系代词，还是关系副词完全取决于从句中的谓语动词。
及物动词后面无宾语，就必须要求用关系代词；而不及物动词则要求用关系副词。
例如：This is the mountain village where I stayed last year.I'll never forget the days when I worked together with you.判断改错1. This is the mountain village where I visited last year.2. I will never forget the days when I spent in the countryside.3. This is the mountain village (which) I visited last year.4. I'll never forget the days (which) I spent in the countryside.方法二：准确判断先行词在定语从句中的成分(主、谓、宾、定、状)，也能正确选择出关系代词/关系副词。
1.Is this museum ___ you visited a few days age?A. whereB. thatC. on whichD. the one2. Is this the museum ____ the exhibition was held.A. whereB. thatC. on whichD. the one例1变为肯定句：This museum is ___ you visited a few days ago.例2变为肯定句：This is the museum ___ the exhibition was held.在句1中，所缺部分为宾语，而where, that, on which都不能起到宾语的作用，只有the one既做了主句的表语，又可做从句的宾语，可以省略关系代词，所以应选D。
而句2中, 主、谓、宾俱全，从句部分为句子的状语表地点，既可用副词where，又因in the museum词组，可用介词in + which 引导地点状语。
而此题中，介词on 用的不对，所以选A。
关系词的选择依据在从句中所做的成分，先行词在从句中做主、定、宾语时，选择关系代词(who, whom, that, which, whose)；先行词在从句中做状语时，应选择关系副词( where 地点状语，when 时间状语，why 原因状语) 。
区分定语从句和同位语从句1．定语从句修饰先行词，它和先行词是修饰关系；同位语从句说明先行词的具体内容，是补充说明的关系(1) The plane that has just taken off is for London. 定语从句(2) The fact that he has been dead is clear. 同位语从句2．定语从句由关系代词或者关系副词引导，关系词在句中充当成分，有时可以省略；同位语从句主要由that引导，在句中一般不做成分；句子也可以由when, where, how, why, whether,what等词引导，充当成分(1) The news he told me is true.(2) The news that he has just died is true.(3) The problem that we are facing now is how we can collect so much money. 定语(4) The problem how we can collect so much money is difficult to solve.3. 同位语从句和先行词一般可以用be动词发展成一个完整的句子，而定语从句不可以(1) The idea that we could ask the teacher for advice is wonderful.(2) The idea was that we could ask the teacher for advice.(3) The fact that the earth moves around the earth is known to all.(4) The fact is that the earth moves around the earth.Exercises1.Mother bought me a dictionary on my birthday, ________made me very happy.A. whatB. thatC. whoD. which2. Loo k at the watch. Don’t you see it is _______ watch ________ Helen lost the other day?A. as the same; asB. the same; asC. the same; whichD. as the same ; that3. ________ is known to everybody, the moon travels round the earth once every month.A. ItB. AsC. ThatD. What4. The weather turned out to be very good, _____ was more than we could expect.A. whatB. whichC. thatD. it5. After living in Paris for fifty years he returned to the small town, _______ he grew up as a child.A.whichB. whereC. thatD. when6. He made another wonderful discovery, ________ of great importance to science.A. which I think isB. which I think it isC. which I think itD. I think which is7. The doctor advised Vera strongly that she sh ould take a holiday, but __________ didn’t help.A. whichB. itC. sheD. he8. ________ is reported in the newspaper, talks between the two countries are making progress.A. ItB. AsC. ThatD. What9.Is this the only reason ______ at the meeting for his carelessness in his work?A. that he explainedB. what he explainedC. why he explainedD. which he explained。
