In this paper I advance an interpretation of Prodicus' conception of the correctness of names or terms. I advance this interpretation through examining a distinction between pleasures and pleasure terms that several ancient authors, most importantly the fifth-century Neoplatonist Hermias, attribute to Prodicus. Since Hermias lived many centuries after Prodicus, it is questionable whether Hermias' testimony is accurate. Consequently, I first present evidence to support the view that Hermias' testimony is accurate. Subsequently, I examine the grounds and context of Prodicus' distinction. I reject the view that Prodicus was interested in drawing distinctions between near synonyms according to standard usage. Instead, I argue that Prodicus' linguistic distinctions follow substantive distinctions between natural kinds.