引导表语从句的关联词有连词：that，whether，if；连接代词：who，whom，whose，what，which；连接副词：when，where，why，how；关系代词what，以及as if，as though，because等连词。如：

The trouble is that I have lost his address.麻烦的是我把他的地址丢了。

You are not who I thought you were.你已不是我过去所想象的人。

That was when I was fifteen.这是我15岁时发生的事。

That’s what I want to stress.这是我想强调的。

It is not as though we were poor.又不是我们家里穷。

注意：表语从句位于主句的连系动词之后，在非正式文体中引导词that可以省略。如：My opinion is（that）things will improve.我的意见是事情会好起来的。