关于 非限定性定语从句

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,