引導表語從句的關聯詞有連詞：that，whether，if；連接代詞：who，whom，whose，what，which；連接副詞：when，where，why，how；關係代詞what，以及as if，as though，because等連詞。如：
The trouble is that I have lost his address.麻煩的是我把他的地址丟了。
You are not who I thought you were.你已不是我過去所想象的人。
That was when I was fifteen.這是我15歲時發生的事。
That’s what I want to stress.這是我想強調的。
It is not as though we were poor.又不是我們家裏窮。
注意：表語從句位於主句的連係動詞之後，在非正式文體中引導詞that可以省略。如：My opinion is（that）things will improve.我的意見是事情會好起來的。