连接表语从句的连接词有：that, what, who, when, where, which, why, whether, how, whoever，whichever ，whatever等。还有如because, as if, as though等。
1.that作引导词
当that引导表语从句时，只起连接作用，不在表语从句中充当任何句子成分,但通常不省略，除了在部分口语句子中。
例如：The fact is that he doesn’t really try.
2.whether作引导词
当表语从句要表达“是否”的含义时，连接词要用whether, 并且绝对不能用if进行替换。
例如：The question is whether the film is worth seeing.
3.连接代词who/whom/whose/which作引导词
当疑问代词用来连接表语从句时，既起连接作用，又充当句子成分。
例如：The problem is who we can get to replace her.
4.连接副词when/where/why/how作引导词
当疑问副词来连接表语从句时，既起着连接作用，同时充当句子成分，一般作状语。
例如：The problem is how we can find him.
5.关系代词what作引导词
what引导表语从句时，既起连接作用，又充当句子成分。
例如：That’s what I want to stress.
