That可以做副词，代词，形容词和连词，但是做连词时是最常见的，也是最难鉴别的，that 用作连词，引导名词性从句,状语从句和强调句。

　　1.that在名词性从句中。

　　①引导宾语从句。及物动词后的引导词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引导主语从句。通常采用it作形式主语的句型。

　　That the earth goes around the sun is known to everyone.

　　(It is known to everyone that the earth goes around the sun.)

　　③引导表语从句。

　　The trouble is that we are short of money.

　　④引导同位语从句。

　　引导同位语从句的that和引导定语从句的that是不同的。前者只起语法作用，在从句中不作任何成分;而后者在定语从句中作主语、宾语或表语。举例说明：

　　The news that he resigned from office surprised us.

　　The idea that he holds is very common nowadays on campus.

　　2. that引导状语从句

　　①引导目的状语从句。

　　Bring it nearer that I may see it better.

　　②引导结果状语从句。

　　What have I done that he should be so angry with me?

　　③引导原因状语从句。

　　I am afraid that I will fail in the driving test.

　　④引导让步状语从句。意为"虽然、尽管"。

　　Difficult that/as the task was, they managed to accomplish it on time.

　　⑤引导条件状语从句。意为"假使、假设"。

　　Supposing that you were in my position, what would you do?

　　On condition that you were lost in the desert, you should ask for help as soon as possible.

　　3. 引导强调句。

　　It is Mrs. White that makes the decision in her family, not her meek little husband.

　　It is an ill wind that blows nobody good.

　　附加：that引导定语从句(做关系代词)

　　Is he the man that wants to see you?

　　The package that you are carrying is about to come unwrapped.