名词性从句，从字面意义上看，它在句子中相当于名字的作用。名词性从句是历年高考的重点和难点也是热点。它的英文名称是Noun clause。名词性从句的功能相当于名词词组， 它在复合句中能担任主语、宾语、表语、同位语、介词宾语等。因此，根据它在句子中不同的语法功能，名词性从句又可分别称为主语从句、宾语从句、表语从句和同位语从句。例如：
1. The trouble is that I have lost his address.
麻烦的是我把他的地址丢了。
2. My suggestion is that we should tell him.
我的建议是我们应该告诉他。
3. You are not who I thought you were.
你已不是我过去所想像的人。
4. The problem is who we can get to replace her.
问题是我们能找到谁去替换她呢。
5. That’s where I first met her.
那就是我第一次遇见她的地方。
6. It isn’t as if you were going away for ever.
又不是你离开不回来了。
7. Now it was as though she had known Millie for years.
现在好像她认识米莉已有好多年了似的。
8. It is not as though we were poor.
又不是我们家里穷。
9. That he is still alive is a wonder.
他还活着，真是奇迹。
10. That we shall be late is certain.
我们要晚了，这是确定无疑的。