同位语从句是对名词的内容给予具体、详细的说明。常在后面接同位语从句的名词有fact, news, idea, truth, hope, suggestion, question, problem, doubt, fear, belief等。同位语从句常用的引导词为that,有是也用when, where 等疑问词。如：

　　The news that the United States was hit by terrorist attacks took the whole world by surprise. 美国受到恐怖主义分子袭击的消息令全世界吃惊。

　　The idea that you can do this work well without thinking is quite wrong. 你认为不动脑筋就能做好这件工作的想法是完全错误的。

　　People used to hold the belief that the earth was the center of the universe. 人们曾认为地球是宇宙的中心。

　　The difficulty lies in the fact that we are short of money. 困难在于我们缺乏资金这个事实。

　　They have no idea at all where he has gone. 他们一点儿也不知道他去哪儿了。

　　注意：同位语从句的that 只是引导词，没有其他语法作用，在句子中不作句子成分，不能省略；而定语从句中的that 除了引导定语从句外，还是定语从句的一个成分，在定语从句中作主语或宾语，作主语时不能省略，作宾语时可以省略。如：

　　The idea that some peoples are superior to others is sheer nonsense. 有些民族优越于其他民族这种想法简直荒谬。(同位语从句)

　　The idea that he proposed at the meeting is sheer nonsense. 他在会议上提出的这个想法简直荒谬。(定语从句)

　　No one is happy with the fact that he found out. 没有人对他发现的事实感到高兴。(定语从句)

　　No one is happy with the fact that he will become their boss. 没有人对他将成为他们的老板这一事实感到高兴。(同位语从句)