Attributive Clauses
定语从句
定语从句：是由关系代词和关系副词引导从句，其作用是作定语修饰主句某个成份，定语从句分为限定性和非限定性从句两种。
1、In their class there are fifteen students who can speak English well.               限定性定语从句
2. In their class there are fifteen students, who can speak English well.             非限定性定语从句

eg. This is the girl (whom) I met yesterdayeg. She sang a song, which we liked very much.
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限定性定语从句和非限定性定语从句区分