从属连词用来引导各种从句.常见的从属连词有：
(1)引导时间状语从句的after,before,when,while,as,until,till,since,as soon as等.
(2)引导条件状语从句的if,unless,once,as long as等.
(3)引导原因状语从句的because,as,since等.
(4)引导目的状语从句的so that,in order that等.
(5)引导让步状语从句的though,although,even if=even though等.
(6)引导结果状语从句的so that,so…that,such…that等.
(7)引导比较状语从句的than,as…as等.
(8)引导名词从句的that,if ,whether等.