名词性从句是英语语法中的重要知识点，可作为主语、宾语、表语和同位语。主要分为四种类型：主语从句，宾语从句，表语从句和同位语从句。各类从句在句子中的作用和结构不同，通常由连词that，whether或if引导。掌握这些从句对英语学习和写作有很大帮助。
主语从句
主语从句在句子中作主语，一般由连词that, whether或者if引导，例如：
- That he is always late annoys me. (他总是迟到这一点让我很恼火。)
- Whether we should go camping or not depends on the weather. (我们是否去露营取决于天气。)
- If you have any questions, please ask me. (如果你有任何问题，请问我。)
宾语从句
宾语从句在句子中作宾语，一般由连词that, whether或者if引导，例如：
- He said that he would come to the party. (他说他会来参加聚会。)
- I don't know whether/ if he is telling the truth. (我不知道他是否在说真话。)
- She asked me if I could help her with her homework. (她问我能否帮她做作业。)
表语从句
表语从句在句子中作表语，一般由连词that或者whether引导，例如：
- The problem is that we don't have enough money. (问题在于我们没有足够的钱。)
- His concern is whether he can finish the project on time. (他关心的是他能否按时完成这个项目。)
同位语从句
同位语从句用来解释或说明名词，一般由连词that或者whether引导，放在名词后面，例如：
- The news that he got the job made me happy. (他找到工作的消息让我很高兴。)
- The fact that she is pregnant surprised everyone. (她怀孕的事实让所有人都感到惊讶。)
