hence:

adv. 因此；今后

Hence, this mother chose to leave the village.

这位母亲因此选择了离开村庄。

henceforth:

adv. 从此以后

Henceforth, you are my legal wife, and I will make you happy.

从今往后，你就是我合法的妻子了，我会让你幸福的。

Henceforth, I hope you won't make such mistakes as you did today.

我希望从现在开始你不要再犯今天这样的错误了。