在英语语法中，连接名词性从句的常用连接词包括"that"、"whether"、"if"、"what"和"who/whom"。这些连接词可以使句子更加完整和清晰，表达出更准确的含义。
以下是连接名词性从句的常用连接词：
1. that
“That”是连接名词性从句的最常用的连接词之一。它可以用来连接主句和从句，引导从句作为名词在句子中充当主语、宾语、表语或同位语等成分。例如：
- I know [that he is coming].
- Do you think [that we should go]?
- His belief [that everyone is equal] is admirable.
2. whether
“Whether”用来引导一个名词性从句，表示两个或多个选择中的某一个。例如：
- I haven't decided [whether to go to the party].
- We’re not sure [whether it will rain tomorrow].
- He asked me [whether I had seen the movie].
3. if
“If”可以用来引导一个名词性从句，表示假设、条件或疑问。例如：
- I don’t know [if he will come].
- [If you have any questions], please ask me.
- [If it rains tomorrow], we’ll stay inside.
4. what
“What”可以用来引导一个名词性从句，作为主语或宾语。例如：
- [What he said] made me angry.
- I don't know [what to do].
- [What I want] is a peaceful life.
5. who/whom
“Who/whom”可以用来引导一个名词性从句，作为主语或宾语。例如：
- I don’t know [who is coming].
- Can you tell me [whom you are talking to]?
- [Whoever finishes first] can leave early.
