名词性从句是英语语法中的重要部分，分为三种类型：主语从句、宾语从句和表语从句。主语从句作为主句的主语，宾语从句作为句子的宾语，而表语从句则作为句子的表语。这些从句通常由连接词如that、whether、who、what等引导。
主语从句
主语从句作为主句中的主语，通常由一个连接词引导，如that、whether、who、what等等。例如：
- That he passed the exam is great news.
- Whether she will come to the party is still uncertain.
- Who will be the next president is a topic of much debate.
宾语从句
宾语从句在句子中作为宾语出现，通常由一个连接词引导，如that、whether、if、who、whom、what等等。例如：
- I believe that you will succeed in your new job.
- She asked me if/whether I had finished my homework.
- He doesn't know what he should do next.
表语从句
表语从句在句子中作为表语出现，通常由一个连接词引导，如that、whether、who、what等等。例如：
- My biggest fear is that I will fail the exam.
- The question is whether we should go or stay.
- Her wish is that everyone would be happy.
