时间从句： when, while, before, after, since, until, as soon as

原因从句： because, since, as

条件从句： if, unless, provided that

让步从句： although, even though, while

目的从句： so that, in order that

结果从句： so...that, such...that

注意： 状语从句是从属结构，不能单独成句（避免句子碎片）。