Every he, or male animal, is of the masculine gender; as, man, hombre; every she, or female, is of the feminine gender; as, woman, mujer. Nouns of inanimate objects or things ending in a, ad, bre, ion, are for the most part feminine; and those terminating in e, i, o, u, on, are masculine. The exceptions, however, are very numerous.

Common nouns ending in o, change it into a to form the feminine; as, son, hijo; daughter, hija. There are some that express their gender by a different word or termination; as, father, padre; mother, madre; bull, toro; cow, vaca; poet, poeta; poetess, poetisa. (See Ollendorff, p. 246.)

Common nouns terminating in an, on, or, add an a to form the feminine; as lion, leon; lioness, leona; shepherd, pastor; shepherdess, pastora.