Definition from Wiktionary, the free dictionary
-ο • (-o)
- (nouns in -ος) ending for accusative singular forms (eg δρόμος, ψήφος); and some vocative singular forms.
- (nouns in -ο) ending for nominative, accusative and vocative singular forms (eg μέτωπο).
- (adjectives) ending for masculine, accusative singular and neuter, nominative, accusative and vocative singular forms.