连词: when, whenever, before, after, while, as, once (一旦),until, (ever) since, as soon as等。
(时间和条件状语从句中表示将来的情况通常用一般现在时。)
eg: When you cross a road, you must be careful.
It will not be long before we meet again.
She comes here every month since she was a child to see her grandmother.
As soon as I know it, I'll tell you.