所谓连接代词和副词,实际上就是我们以前学过的疑问代词和副词,如who, whose, whom, what, which, when, where, why, how以及由how构成的词组.但必须注意两点,一是它们在构成疑问句时叫疑问词,引导宾语从句时称作引导词.一是它们和that不一样,在从句中有含义,担任相关的句子成分,所以不能省略,另外,它们须放在宾语从句之首,宾语从句必须是陈述句结构.
引导名词性从句的连接词可分为三类：
连接词：that,whether,if 不充当从句的任何成分）
连接代词：what, whatever, who, whoever, whom,
whose, which.
连接副词：when, where, how, why
不可省略的连词：
1. 介词后的连词
2. 引导主语从句和同位语从句的连词不可省略.
That she was chosen made us very happy.
We heard the news that our team had won.
比较：whether与if 均为"是否"的意思. 但在下列情况下,whether 不能被if 取代：
1. whether引导主语从句并在句首
2. 引导表语从句
3. whether从句作介词宾语
4. 从句后有"or not"
Whether he will come is not clear.
大部分连接词引导的主语从句都可以置于句末,用 it充当形式主语.
It is not important who will go.
It is still unknown which team will win the match.
