that名詞性從句
1.引導賓語從句。及物動詞后的引導詞that可省略。
I didn't expect (that) he could win the championship.
The teacher pointed out that Tom was not working hard enough.
2.引導主語從句。通常采用it作形式主語的句型。
That the earth goes around the sun is known to everyone.
（It is known to everyone that the earth goes around the sun.）
3.引導表語從句。
The trouble is that we are short of money.
4.引導同位語從句。
引導同位語從句的that和引導定語從句的that是不同的。前者只起語法作用，在從句中不作任何成分；而后者在定語從句中作主語、賓語或表語。舉例說明：
The news that he resigned from office surprised us.
The idea that he holds is very common nowadays on campus.