3、引导连词:that, whether, if, as if。
有词义,在从句中担任成分,如主语、表语、宾语、或定语等。
有词义,在从句中担任成分,作状语。
that 无词义,在从句中不担任成分,有时可省略;if (whether), as if虽有词义,但在从句中不担任成分。
1、连接代词:who, whose, whom, what, which
2、连接副词:when, where, why, how