Jealousy is feeling like something or someone belongs to you. You feel that you deserve, and don't want someone else to have what belongs to you. Is it because a person feels they lack or are insufficient without? Jealousy could be a lack of trust as well.
When something, someone truly belongs with you though then it's a very normal emotion when deprived of the deserve.
Otherwise it's envy and that's not right.
Envy is wanting something, someone that's not yours.
That's how I see it anyways.
I think jealousy is a warning sign. It could be totally unwarranted. It could be justified though. Envy there is no excuse for.
Of course people define things differently whereas jealousy means something much worse.
I say set it free and if it comes back to you willfully, and faithfully then you really got something.