英语语法：限制性定语从句与非限制性定语从句的区别

　　1. 形式上，非限制性定语从句往往用逗号隔开。

　　2. 语法上，非限制性定语从句一般不用that.

　　3. 语义上，限制性定语从句与先行词关系紧密，起限定作用，如果去掉了这个定语从句，整个句子就不完整或者会改变意思;而非限制性定语从句与先行词关系不是很紧密，对先行词起补充说明或描述的作用。

　　This is the book I like best. 这就是我最喜欢的那本书。

　　Beijing, which has been Chinas capital for more than 800 years , is rich in cultural and historic relics. 北京是中国八百年之久的古都，它有着丰富的文化和历史遗产。

　　4. 翻译时，限制性定语从句可译为一句(较短的一般译为的字结构);而非限制性定语从句可译为两句。(见上句翻译)

　　比较: He has a sister, who is a musician.

　　He has a sister who is a musician.

　　引导非限制性定语从句的关系代词，指人时用who, whom, whose , 指物时用which , whose; 关系副词when，where, why, etc.

　　1. He studied hard at school when he was young, which leads to his success in his later life.

　　2. Toms father, who arrived just now, is a famous scientist.

　　3. They set up a separate state of their own, where they would be free to keep Negroes as slaves.

　　4. He was proud, which his brother never was.