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。