连接定语从句的关联词,在定语从句必须充当一个句子成分,所以不能称为连词,只能称为“关系代词”或“关系副词”.如何选择呢?记住：关系代词可以充当主语,表语,宾语.而关系副词只能充当状语.例如：
1.This is the school which I visited three years ago.在定语从句中 which 是关系代词,充当宾语.
2.This is the school where I studied three years ago.在定语从句中 where 是关系副词,充当地点状语.