三.限制性定语从句与非限制性定语从句

1.限制性定语从句说明先行词的情况，对先行词起限定作用，与先行词关系十分密切，不可用逗号隔开，也不可省略，否则全句意义就不完整。如：

This is the telegram which he refers to.

Is there anything (that) I can do for you?

2.非限制性定语从句只是对先行词作补充说明，没有限定作用，它与先行词的关系比较松散，因而不是关键性的，如果省略，原句的意义仍然完整。这种从句在朗读时要有停顿，在文字中通常用逗号与主句隔开。如：

This note was left by Tom, who was here a moment ago.

As a boy, he was always making things, most of which were electric.

引导非限制性定语从句的关系词有：who, whom, whose, which, when 和 where，不可以用that和why。

另外，非限制性定语从句从意义上讲，相当于一个并列句，在口语中使用并不普遍，在日常生活中，人们通常用并列句或简单句来表达。如：

I told the story to John, who later did it to his brother.

= I told the story to John, and he later told it to his brother.

Yesterday I happened to see John, who was eager to have a talk with you.

= Yesterday I happened to see John and he was eager to have a talk with  you.

3.两种定语从句的内涵不同，限制性定语从句具有涉他性，而非限制性定语从句具有唯一性，这在理解和翻译时应特别注意。试比较：

All the books there, which have beautiful pictures in them, were written by  him.

All the books there that have beautiful pictures in them were written by  him.

His brother, who is eighteen years old, is a PLA man. (只有一个)

His brother who is a PLA man is eighteen years old. (不止一个)

4.有时，非限制性定语从句所修饰的不是某一个词，而是整个主句或是主句中的一个部分，这时一般采用which或as来引导。如：

He passed the exam, which/as he hoped he would.

注：(1)as引导的从句可以放在主句之前，而which引导的从句只能放在主句之后。

They are hollow, which makes them very light.

As is known to all, Taiwan is a part of China.

(2)从意义上讲，which指前面主句的内容;而as指代的是作为一般人都知道的常识性的东西，因此常译成“就象… …那样”。

(3)如果定语从句的内容对主句的内容起消极作用，则用which，而不用as，如：

She stole her friend’s money, which was disgraceful.

He tore up my photo, which upset me.

5.在正式文体中，以the way为先行词的限制性定语从句通常以in which或 that 引导，如：

The way in which you answered the questions was admirable.

但在非正式文体中，人们通常省略in which或 that :

The way (in which) he spoke to us was suspicious.

I don’t like the way (that) you laugh at her.