名詞子句主要功用是當主詞、受詞及補語，引導名詞子句的連接詞為that及wh之疑問詞。關於名詞子句的重要細節如下：
1. 名詞子句當主詞時，動詞要用單數。
例：
1. That honesty is the best policy is true.
2. What happened to him during those years has puzzled us.
2. that 所引導的名詞子句若當動詞之受詞，則 that 可以省略。
例：
1. I think (that) they all will come.
2. I believe (that) you will like the story.
3. that所引導的名詞子句前面不能有介系詞。
例：
1. I’m sure of that he is a French. (of要去掉)
2. We insisted on that he should come back soon. (on要去掉)
4. wh 所引導的名詞子句雖然語意上是表達疑問或不確定，但仍然不可用疑問句的形式。下列例句要做修改：
例：
1. I don’t know where is he.
改為→I don’t know where he is.
2. Do you know when will he come back?
改為→Do you know when he will come back?
3. They asked him why did he do it.
改為→They asked him why he did it.
註：直接問句仍然用疑問句形式。
例：Where is John?
“What does he do”John asked.
5. wh 所引導的名詞子句可簡化為不定詞片語的結構，但 why 例外。
例：
1. I haven’t decided whether I should take that course.
→I haven’t decide whether to take that course.
2. I don’t know where I can find him.
→I don’t know where to find him.
3. The meeting emphasized how people could stop smoking.
→The meeting emphasized how to stop smoking.
6. that 所引導的名詞子句可簡化為動名詞片語之結構，簡化的步驟為：(a)去掉that，(b)主詞改為所有格，(c)動詞改為動名詞。
例：
1. That David will come tomorrow excites all of us.
→David’s coming tomorrow excites all of us.
2. We are interested that he becomes an actor.
→We are interested in his becoming an actor.
3. I am glad that you tell me the truth.
→I am glad of your telling me the truth.
英文文法
