在復合句中充當表語。
1. that在引導表語從句時無含義，不作成分，通常不省。
?1)表示事實、真理等的實際內容。
? ? The fact is that he is lying.
? ? The odds are that he will not do it.
?2)表示某人的意見、信念等的實際內容。
? ? Our belief is that things will improve.
? ? The trouble is that we are short of money.
2. whether引導表語從句（不可用if)
? ? His first question was whether holmes had arrived yet.
? ? The question is whether people will buy it.
3.連接代詞引導的表語從句。
? ?This is what i want.
? ?The question is who can be chosen to be manager of the company.
? ?My question is which of them is better.
4.連接副詞引導的表語從句。
? ?The problem seemed how we could make him understand it.
? ?The question is where we should go.
5. as if, as though引導的表語從句（常用虛擬語氣）
? ?He looks as if he were angry.
? ?It looks as if it's going to rain.