A conch is a large sea snail with a thick, twisted shell; people also call the empty shell a conch. It lives in warm seas. In some places you eat the animal; in others you polish the shell or blow it like a horn — the sound carries a long way. You will hear two pronunciations: a final k sound (like “conk”) and a ch as in “church.” Both are used. The word was borrowed from Latin concha, from Ancient Greek κόγχη (kónkhē, a mussel or cockle; a shell-like hollow). It is a doublet of concha, a more technical word for a shell-shaped hollow (for example in the ear). Architects have also used conch for a half-dome. Those uses are specialist. Though actually, English also uses conch as a verb in one factory corner: chocolate makers conch chocolate, working it for hours in a machine so it becomes smooth. That machine was named for a shell-like shape. You will not hear this sense at the beach. For most learners the living word is the sea animal and its shell.