Common Gender.—Many nouns denoting persons are either masculine or feminine. Thus, ὁ παῖς boy, ἡ παῖς girl, ὁ θεός god, ἡ θεός (ἡ θεᾱ́ poet.) goddess. So with names of animals: ὁ βοῦς ox, ἡ βοῦς cow, ὁ ἵππος horse, ἡ ἵππος mare.
a. Some names of animals have only one grammatical gender without regard to sex, as ὁ λαγώς he-hare or she-hare, ἡ ἀλώπηξ he-fox or she-fox.