一.四大条件状语从句

　　1 时间状语从句 【adverbial clause of time】：

　　常用引导词：When, while, as, after, before, as soon as, since, till
http://toefl.xiaoma.com/beikaoce ... 32307.html?seo=bgz3
　　2 原因状语从句 【adverbial clause of cause】：

　　常用引导词：because, since, as, for

　　特殊引导词：seeing that, now that, in that, considering that

　　3 条件状语从句 【adverbial clause of condition】

　　常用引导词：if, unless,

　　特殊引导词：as/so long as, only if, providing/provided that, supposing that, in case that, on condition that

　　4 让步状语从句 【adverbial clause of concession】

　　常用引导词：though, although, even if, even though

　　特殊引导词： as(用在让步状语从句中必须要倒装)，while(一般用在句首)，no matter …, in spite of the fact that, while, whatever, whoever, wherever, whenever, however, whichever