定语从句 ●关系词的意义及作用 : 定语从句一般都紧跟在它所修饰名词后面，所以如果在名词或代词后面出现一个从句，根据它与前面名词或代词的逻辑关系来判断是否是定语从句。

被定语从句所修饰的名词或代词叫做“先行词”。引导定语从句的词叫“关系词”。关系词有两个作用： 一、引导定语从句。 二、代替先行词在其引导的定语从句中充当一定的句子成分。 理解和牢记这两条概念，弄清楚关系词在定语从句充当什么成分，是掌握定语从句的关键。

主要用于非限制性的定语从句和such…as, the same…as, as…as,结构中。 ●关系词的选用与判断: 关系词　主语　　宾语　表语　　　定语　　　状语　　　 that　　人/物　　人/物　√　　 　×　　　　　 × 　　　　 which　物　　　　物　 ×　　　　×　　　　 × who　　人 　　　　× 　×　　　　× 　　　　× whom　×　　　　人　 ×　　　　×　　　　　× whose　×　　　×　　 ×　　　　人/物　　　 × when　×　　　　×　 ×　　　　×　　　　　√ where　×　　　×　　 ×　　　　×　　　　　√ why　　×　　　×　　 ×　　　　×　　　　　√ as　　　　 主要用于非限制性的定语从句和such…as, the same…as, as…as,结构中。

二、关系词的选用 1.先行词为all,everything,nothing等不定代词，代替物时，定语从句that用引导。 注：something后一般用which。 Is there anything that you want to explain? In 1898 they declared that they believed there was something in nature which gave out radiation.

2.先行词前有形容词最高级、序数词或only,very,none,no,little,few,much等修饰时定语从句用that引导。 This is the only reason that I can say. This is the first step that can be taken. It is the best one that you may choose.

3.way后面的定语从句，引导定语从句有三种情况： a. 在比较正式的文体中用in which； b.一般情况下用that； c. In which和that省去。 I was struck by the beauty of the way in which she stood. It was clear that the speaker now trusted Tom from the way in which these words were said.

b. Lincoin asked the people to think of slavery in the way that these men did. Mary, there is one way that you could stop others talking about you and criticizing you. c.That’s the way I looked at it. The assistant who served her did not like the way she was dressed.

4.先行词是表示地点的名词时（country, school, room…），而关系词代替先行词在定语从句中充当地点状语，一般用where引导定语从句。也可以用介词＋which的结构。值得注意的是which前介词的选择是根据先行词与介词的搭配关系而定。 The room where(=in which) he used to live has now been turned into a museum. The desk where(=on which) I put my bag is his. This is the school where(=in which) I joined the Party. 关系词的选用与判断（续）

5.先行词是表示时间的名词（year, month,day,night…），而关系词代替先行词在定语从句中充当时间状语，一般用when引导定语从句。也可以用介词＋which的结构。值得注意的是which前介词的选择是根据先行词与介词的搭配关系而定。 在掌握第4、第5条时应特别注意：介词的位置变化以及相应的关系词的变化。请分析下面两个句子。

①那就是他工作的大学。 ┏ at which he works. ┣ which he works at. That is the college ┣ where he works. ┣ that he works at. ┗ he works at.

②它出生的那一天是1952年8月20日。 ┏ on which he was born ┣ which he was born on The day ┣ when he was born was　Aug.20,1952. ┣ that he was born on ┗ he was born on

除了第4、第5条中when，where可以用介词＋关系词这种用法外。还有其他情况也可以用这种结构。即：介词＋which。或介词＋whom。请看下面例句： This is the classmate with whom I’ll go to the cinema. The subject in which I’m most interested is English. We can see the method by which the computer works. 在这种结构中，介词与先行词组成短语，在从句中充当句子成分，因此介词的选用时受到一定限制的，仍然根据先行词与介词的搭配关系而定。

三、关于as引导定语从句的问题 as引导定语从句主要用于非限制性定语从句和the same…as，such…as，as…as的结构中。 1.as与which都可以引导一个非限制性定语从句，并代表前面整个句子或主句中的表语。 He married the girl，as (which) was natural. He seemed a foreigner , as (which) in fact he was. 不同的是：as引导的定语从句可以前置，而which不行。 As was natural, he married the girl.

2.在the same…as, such…as, as… as 结构中，same ,such, as之后应是名词或形容词＋名词。 We are facing the same problems as we did years ago. Some people have no doubt that their cat understands as many words as a dog does. We hope to get such a tool as he is using.

We are facing the problems which we faced years ago. 这三种结构也可以用which改写。但要去掉这种结构，不能直接用which代替as。以上三句分别可以改写成： Some people have no doubt that their cat understands the words which a dog understands. We hope to get the tool which he is using.

3.the same…as与the same…that引导的定语从句在意义上的区别是：前者修饰的是与原物同样的；而后者修饰的就是先行词同样的东西。是比较： This is the same watch as I lost. 这和我丢失的那一只表一样。（不是同一只） This is the same watch that I lost. 这就是我丢失的那一只表。（同一只）

●注意事项 1.一般说来，除了用定语从句解释名词或泛指外，先行词前应有定冠词the。 2.在限制性定语从句中 which, whom, that充当宾语时，可以省略。而在非限制性定语从句中 whom, who, which不能省略。 3.在含有非限制性定语从句的复合句中从句与主句之间应该用逗号隔开。

4.定语从句与同位语从句的区别。首先看引导从句的关系词that是否在从句中充当句子成分。如果在从句中充当主、宾、表，则是定语从句。再看that前的名词是否是一些需要有内容的名词，如：idea, fact, thought, news等。后面的从句是说明其内容的，（这个名词在后面的从句中部充当任何成分），这个从句则是同位语从句。 He expressed the hope that he has had for many years. hope在从句中不充当句子成分，又加上后面从句是说明hope的内容的，因此时同位语从句。

5.the reason why(=for which)是由why或for which引导的定语从句。而the reason that也是that引导的定语从句。that往往省略。 This is the reason why he was late.　=This is the reason (that)he was late.

6.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，定语从句用that引导。 Who is the man that is standing by the door? Which of the two cows that you keep produces more milk? 7.先行词为人和物作并列成分时，定语从句用that引导。 John and his dog that were here a moment ago disappear now.

8.不论人或物在定语从句中作表语时，用that引导定语从句，而that通常省掉。 He is no longer the man that he was. 9.“one of＋可数名词复数”引导的定语从句中,谓语动词应用复数；而“one of＋可数名词复数”前有the，only或the only修饰，定语从句中的谓语动词用单数。 He is one of the students who study very hard at school. He is the(only/the only) one of the students who studies very hard at school.