pontus

Pontus, ponti is second declension masculine, borrowed from Greek pontos. It is a poetic word, not the everyday one: mare is the sea you sail on and trade across, pontus is the deep, the open water, the sea as a force in epic. Virgil and Ovid use it constantly and Caesar hardly at all, so its frequency in a corpus tells you something about the texts rather than the language.

Two traps. Pontus is not pons, pontis, "bridge", though the accusative pontem and the genitive ponti sit uncomfortably close. And capitalised Pontus is the region on the Black Sea coast, the province Pliny governed and the homeland of Mithridates, which is where Pontic and pontifex confusions begin. Pontifex, incidentally, belongs with pons, not with the sea.