英语八大从句及其引导词如下：

时间状语从句

引导词：

when, while, as, before, after, since, until, the moment, the second, every time, the day, immediately, directly, no sooner…than, hardly…when, scarcely…when

地点状语从句

引导词：

where, wherever, anywhere, everywhere

原因状语从句

引导词：

because, since, as, for, seeing that, now that, in that, considering that, given that

结果状语从句

引导词：

so…that, such…that, to the degree that, to the extent that, to such a degree that

目的状语从句

引导词：

so that, in order that, in case, if only

条件状语从句

引导词：

if, unless, whether（whether…or not）, as long as, in case, if only, provided that

名词性从句

引导词：

that, what, who, whom, whose, which, that引导的主语从句，where, when, why引导的宾语从句，if, whether引导的主语从句

定语从句

引导词：

who, whom, whose, which, that, as引导的限制性定语从句，who, whom, whose, which, that引导的修饰人或物的定语从句

这些引导词在英语语法中起着至关重要的作用，帮助构建复杂的句子结构，使句子表达更加清晰和准确。