同位语从句：We haven’t yet settled the question where we are going to spend our summer vacation.到哪儿去度暑假,这个问题我们还没有决定.where we are going to spend our summer vacation=the question,说明the question的具体内容.
定语从句：Shanghai is the city where I was born.先行词是the city,关系副词引导定语从句,在从句中作地点状语,相当于in which.可把先行词带入从句,即：I was born in the city.