引导定语从句的关系代词有that, which, who, whom和whose。若先行词是人且在从句中作主语时，关系词选用who或that; 作宾语时可选用whom或that，且常可省略。若先行词为物且在从句中作主语或宾语时，关系词则用which或that；作宾语时可省略。whose既可指人又可指物，在从句中作定语。例如：

　　1. The boy who / that told me the news has left.

　　2. A clock is a machine that / which tells us the time.

　　3. The man (who / whom / that) you talked about just now is my friend.

　　4. The students whose home are far away live in the school.

　　由此可见，定语从句关系词的选择并不难，关键是弄清先行词是人还是物，在从句中作什么成分以及句式结构等。但若先行词在从句中作相同的成分，引导词又该如何判断呢？

　　一、 先行词为物时，which与that的区别。

　　在下列情况下，通常只用that。

　　1. 当先行词为none, one, few, little, all, many, much, every, something, everything, anything, nothing时。例如：

　　She did all that she could to help him.

　　Is there anything else that you require?

　　2. 当先行词被some, every, little, few, many, much, all, any, no, none等词修饰时。例如：

　　There is little water that you can drink.

　　You can take any seat that is free.

　　3. 当先行词被the same, the last, the only, the right, the very等词修饰时。例如：

　　It’s the last place that we want to visit.

　　This is the very film that we enjoy.

　　4. 当先行词被序数词或形容词最高级修饰时。例如：

　　This is the first exam that we have this term.

　　This is the best novel that I have read.

　　5. 当先行词既有人又有物时。例如：

　　He talked happily of the men and the book that interested us.

　　6. 当主句是which引导的特殊疑问句时。例如：

　　Which of the books that are on the desk moved him?

　　在下列情况下只用which。

　　1. 当关系代词前使用介词时。例如：

　　That was the train by which they went to Jinan.

　　2. 当先行词本身是that时。例如：

　　The predicate(谓语) is that which is said of subject (主语)。

　　3. 在非限制性定语从句中。例如：

　　Football, which is a very interesting game, is played all over the world.

　　4. 当指物的关系代词被指人的短语隔离时。例如：

　　The cat beside the girl which is lovely was bought yesterday.

　　二、 先行词为人时，who与that的区别。

　　1. 当先行词在从句中作表语或主句是以who引导的特殊疑问句时，关系词用that。例如：

　　He isn’t the man that he used to be.

　　Who is the man that is standing there?

　　2. 若先行词为he, she, those, anyone等表示一类人的词时，关系词一般用who。例如：

　　He who invited me to the party is my brother.

　　Anyone who wants to see the film please let me know.

　　(文/朱孔仁；英语辅导报初四普及版04—05学年度第19期；版权归英语辅导报社所有，独家网络合作伙伴新浪教育，未经许可，不得以任何形式进行转载。)