一、只有少数名词可以带同位语从句。

　　从语义上看，同位语从句说明前面被修饰名词的内容，所以被修饰名词往往具有概括意义，中学英语中常见的有：advice, answer, belief, doubt, fact, hope, idea, message, news, order, promise, possibility, problem, question, report, reply, suggestion, thought, truth, wish等，例如：
　　1．We heard the news that our team had won.
　　2. There is no doubt that the prices will go down.

　　二、同位语从句要有引导词。 引导同位语从句的词有that, whether, how, when, where, why,. who等。引导词的选择是同位语从句的一个"常考点"。选用哪一个引导词，主要依据引导词的词义（注意：that无词义）和同位语从句的语义。
　　1．We expressed the hope which Mr and Mrs Smith would come to Visit China the next A B C D year.(有一处错误) 答案：A, which应改为that。
　　2．The question_____we had enough money for the research up at yesterday's meeting. A. that B. what C. whether D. where 答案：C。全句意思为：昨天的会议提出了我们是否有足够的科研资金的问题。

　　三、同位语从句要用陈述语序。

　　参见上面的例句和考例。

　　四、同位语从句时态受主句时态影响。

　　当主句是过去时态时，从句若不是表示客观真理，则必须用一般过去时，过去进行时，过去将来时或过去完成时；若从句表示客观真理，则只用一般现在时，试比较：
　　1．There was the report that the man had been killed in the Second World War.
　　2. There was the theory long long ago that the sun moves around the earth.