定语从句的分类
定语从句的分为限定性定语从句与非限定性定语从句。
定语从句的分为限定性定语从句与非限定性定语从句。限制性关系从句从语义上看，主要起限定作用，修饰特定的人或事物，如果去掉限制性定语从句，整个句子表意会不完整甚至不通顺；从结构上看，限制性关系从句常紧跟先行词，并且同先行词之间一般不加逗号分隔（但不是绝对的）。
非限制性关系从句从语义上看，主要起补充说明的作用，有时相当于一个并列分句或状语从句，可以表达原因、目的、结果、条件、让步等意义。
例句：
1、He is a man who never breaks his word.
2、He is the man whom I think to be nice.
3、The dog which won the race is John's.
4、The letter that I received yesterday was from my brother.
5、Dr Lee, who had read through the instructions carefully before doing his experiments, did not obtain satisfactory results.
6、The government, which promises to cut taxes, will be popular.
7、There were very few passengers who escaped without serious injury.
8、This is the building whose windows(=the windows of the building) were all painted green.
9、A teacher is a person whose duty(=the duty of a teacher) is to teach.
10、I called him by the wrong name, for which mistake I should apologise.
