状语从句用来修饰主句中的动词，副词和形容词的从句叫状语从句。根据其含义状语从句可分为时间状语从句，地点状语从句，条件状语从句， 原因状语从句，结果状语从句，比较状语从句，目的状语从句，让步状语从句。1. 时间状语从句(1)时间状语从句常用when, as, while, before, after, since, till, until, as soon as等连词来引导。.It was raining hard when got to school yesterday.While he was doing his homework, the telephone rang.(2)在时间状语从句里，通常不用将来时态，用现在时态表示将来的动作或状态。.Ill ring you up as soon as I get to New York.(3)在带有till或until引导的时间状语从句的主从复合句里，如果主句用肯定式，其含义是“一直到时”，谓语动词只能用延续性动词。如果主句用否定式，其含义是“直到才”, “在以前不”, 谓语动词
