一、基本概念：
在复合句中，修饰某一名词或代词的从句叫定语从句。
Do you know the man who spoke at the meeting just now?
That is the house where he lived ten years ago.
定语从句所修饰的词叫先行词；定语从句一般用关系代词或关系副词来引导，关系词放在先行词与定语从句之间起连接作用，同时又作从句中的一个成分。
引导定语从句的关系代词有：that, who, whom, whose, which，as
关系副词有：when, where, why.
二、关系词的用法：
（一）关系代词的用法：
1．作主语用who, which和that, 如：
He is the man who/that lives next door.
The train which/that has just left is for Shenzhen.
2．作宾语用whom, who, which, that, 如：
The man (whom/who/that) we have just seen is a famous writer.
Where is the book (which/that) I bought last week?
