1．定义：
   用作同位语的从句叫做同位语从句。
2.用法：
   同位语从句的先行词多为fact, news, idea, thought, question, reply, report, remark等，关联词多用从属连词。
   如： They were all very much worried over the fact that you were sick.
   注：
  同位语从句偶尔由从属连词whether引导。
   如：I have no idea whether he’ll come or not.我不知道他是否来。
   连接代词who, which, what和连接副词where,when, why, how亦可引 导同位语从句。
        The question who should do the work requires consideration.谁该干这项工作，这个问题需要考虑。
        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。