状语从句是英语语法中的一种从句，用于修饰主句中的动词、形容词、副词等，提供时间、地点、原因、条件、目的、结果、让步、方式和比较等方面的信息。以下是状语从句的九种类型及其引导词：

时间状语从句

引导词：when, whenever, while, as, before, after, until, till, not…until, since, ever since, once, as soon as, the moment, the second, immediately, instantly, directly, hardly…when, scarcely…when, no sooner…than

地点状语从句

引导词：where, wherever

原因状语从句

引导词：because, since, as, for, now（that）

目的状语从句

引导词：so that, in order that

结果状语从句

引导词：so that, so…that, such…that, such that

条件状语从句

引导词：if, unless, once, in case, on condition that, supposing, provided that, for fear that

让步状语从句

引导词：though, although, as, whether…or, while, no matter what, no matter how, no matter when, no matter where, no matter why

方式状语从句

引导词：as, the way

比较状语从句

引导词：than

状语从句通常由连词（从属连词）引导，也可以由词组引起。它们在句子中充当修饰成分，使句子表达更加丰富和精确