湖南长沙市第二十一中学 刘纯南
定语从句是高中阶段英语教学的重点难点之一。学生在学习定语从句时感到最棘手的问题之一是介词的使用，这表现在两个方面：一是他们不知道如何使用介词，二是他们不知道如何进行“介词 + 关系代词”与关系副词之间的互换。所以，学生要学好定语从句应注意如下几点：
1 ．正确使用介词。定语从句中介词的使用分为两种情况，一是与定语从句中谓语动词的搭配使用，二是与先行词的搭配使用。例如：
The person about whom they are talking is our math teacher.
Can you tell me the date on which you were born?
前者 talk about 属于固定搭配，后者 on 与表示某一天的名词搭配。
有时介词的使用需要根据句子的意义而定。例如：
His glasses, without which he could see nothing, fell on the ground and broke.
His glasses, with which he saw very clearly, fell on the ground and broke.
2 ．介词的位置。介词在定语从句中的位置一般有下面的规律可循：
1 ）位于关系代词前面。与先行词搭配的介词一般只能放在这个位置。例如：
He built a telescope through which he could study the sky.
The house besides which there is a big tree is Li Hong's.
2) 位于定语从句的谓语动词后面。像 look after, look for, take care of, come across, send for, call on, come about, long for, hear from, get through 这样的短语动词，介词和动词不能拆开，故介词不能放到关系代词之前。在这种情况下关系代词可以省略。例如：
The doctor (that/who/whom) you send for has not come.
The girl (that/who/whom) I came across in the street yesterday is a friend of mine.
The chance (that/which) I longed for has come at last.
3) 位于关系代词之前或者位于定语从句的谓语动词之后。在 talk about, speak to, live in, borrow from, lend to, wait for, work with 这些动词与介词搭配中，介词和动词可以分开使用，所以介词在定语从句中可位于关系代词之前，也可以位于从句的谓语动词之后。例如：
Do you know the woman to whom I spoke just now? 也可以说：
Do you know the woman (that/who/whom) I spoke to just now?
在口语中，这样的介词一般放在从句的谓语动词后面，关系代词也可以省去；在书面语中，介词一般置于关系代词之前。
3 ．关系副词 where, when, why 均可用“介词 +which ”来替换。例如：
The school where/in which I work is a key school.
October 1, 1949 was the date when/ on which the People's Republic of China was founded.
Can you tell me the reason why/for which you were late today?
但是，有些“介词 +which ”就不能用关系副词来替换。例如：
The school near which there is a big library is a key school.
Can you see the year, by which China will become one of the most powerful countries in the world?
4 ．关系代词 whose 引导的定语从句可以用“ of which/whom ”来替换。例如：
The book whose colour is red is mine. = The book the colour of which is red is mine.
The man whose right leg is lame is a famous singer. = The man the right leg of whom is lame is a famous singer.
5 ．先行词为表示交通工具的名词时，只能用“ in/on which ”而不能用“ by which ” 引导定语从句，这是由于这些名词前带有 a, an, the, this, that, one's 等限定词。例如：
Tom's father has bought a car in which he goes to work.
Is that the train on which you went to Shanghai the year before last?
注意下面这个句子中 from where 的用法：
We stood by the window from where we could see the tall building.
摘自 中学英语园地
