连词起连接词与词、短语与短语及句子和句子的作用。
它本身在句子里不单独做句子成分。连词主要包括并列连词和从属连词。并列连词:是用来连接语法地位相同的结构、相同的单词、短语及句子。并列连词有:and, but, or, nor, so, for yet, however, as well as, both...and, not only...but also, either...or, neither...nor, still,从属连词:用来引导状语从句。初中阶段常用的从属连词有:after, when, before, as, while, since, until, till, if, unless,, because, than, that, whether, so that, in order that, as if, although, as...as, such...that, in case that。