Genus
Grammatical gender correlates only partially with sex, and almost exclusively when it relates to humans and domesticated animals. Even then, those correlations may not be consistent: nouns referring to adult males are usually masculine (e.g "father, brother, priest"), nouns referring to adult females (e.g. "mother, sister, priestess") are usually feminine, but diminutives may be neuter regardless of referent, as in both Greek and German. Gender may have also had a grammatical function, a change of gender within a sentence signaling the end of a noun phrase (a head noun and its agreeing adjectives) and the start of a new one.