Mortals

Technically, it means any creature that can die. By that definition even gods can be considered mortals for they can be killed. It’s instead used to mean creatures that can die of old age. This can also include many elementals. It’s usually used to refer to Natural Creatures in common parlance, but there are a few Natural Beings that do not, in fact, die from age. Immortals, by definition, do not die of old age hence their name.