before放在句首的用法？

before在句首和句中一样,没有特别的规则.

before的两个主要用法：1.介词,后跟名词或者动名词,即doing的形式.2.连词,后跟时间状语从句,表示先后关。

Before I could say a word, she had stormed out of the room. 不等我说一句话，她就冲出了房间。

It still took seven years before they finally got married. 过了七年他们才最终得以成婚。