Just as asynchronous means not synchronous, atheist means not a theist, apostate means not a postate and apostle means not a postle, amine (pronoun) means not mine.
Thus, if something is yours I could say that it is amine. However, the collection of amine things is a broader set than the collection of things that are yours. For example, stuff belonging to the weird guy down the street would be amine for both me and you.
If you, without permission, have something in your possession that is, to you, amine, that’s called theft. You could go to jail for that.
If you have something of yours in your possession that’s atheft or, alternatively, ownership. You can’t normally be sent to jail for that. However, be warned that even with the thing of your own being in your possession, you can still go to jail for beating the crap out of someone for no reason, but that’s something completely different.