在英语语法中，名词性从句是指在句子中充当名词的子句。名词性从句连接词是用来引导名词性从句的词汇，它们的作用是把从句和主句连接起来，构成一个完整的句子。
以下是常见的名词性从句连接词及其用法：
- that：可以引导主语从句、宾语从句、表语从句和同位语从句。例如：
- I know that she is coming.
- He said that he was tired.
- The fact that she passed the exam surprised everyone.
- whether/if：可以引导主语从句和宾语从句。不过，whether通常用于“是否”的情况，而if则更常用于条件句。例如：
- I don't know whether/if he will come.
- She asked me whether/if I had finished the project.
- who/whom/whose：可以引导主语从句、宾语从句和表语从句。例如：
- He is the man who/whom I met yesterday.
- Do you know whose bag this is?
- I wonder who/whom she is waiting for.
- where：可以引导表语从句和定语从句。例如：
- This is the place where we first met.
- The city where she lives is very beautiful.
- when：可以引导表语从句和定语从句。例如：
- The time when we met was very special.
- Do you remember the day when we went to the beach?
以上是名词性从句连接词的常见用法。在使用时，需要注意选择合适的连接词，并正确使用从句的语序。掌握这些连接词的用法，有助于提高英语语法水平，让我们的英语表达更加准确自然。
