The Attributive Clause (定语从句）（一）定义：在复合句中，形容词性从句，修饰前面某一名词或代词从句叫定语从句。被定语从句修饰词叫先行词引导定语从句词叫关联代词或关联副词
Mary is a beautiful girl.
形容词作定语
Mary is a girl who has long hair.
句子作定语,修饰girl, 叫做定语从句
Mary is a girl.
Mary has long hair.
合并为一个句子
Mary is a girl who has long hair.
先行词
关联词，引导词
定语从句
Mary is a girl who has long hair.
关系代词
关系副词
which, who, whom, whose, that
Where, when，why