communis

Communis, commune is a third declension adjective of two terminations: one form for masculine and feminine, another for neuter. Ablative singular communi, genitive plural communium. What it is shared with goes into cum with the ablative, or into a plain dative or genitive - nihil commune cum illis, or hominibus commune.

Its opposite is proprius, "one's own", and the pair is the backbone of Roman legal and ethical writing. Two traps. Classical communis can mean "affable, unstuck-up" of a person, a compliment. And in the Vulgate, translating Greek koinos, it flips to "unclean, profane" - the food Peter refuses in Acts is communis, and reading that as "ordinary" loses the whole point of the vision.