A
cognomen (, ; Latin plural
cognomina;
con- "together with" and
(g)nomen "name") was the third name of a citizen of
ancient Rome, under
Roman naming conventions. Initially, it was a
nickname, but it lost that purpose when it became hereditary. Hereditary
cognomina were used to augment the second name (the
family name, or clan name) in order to identify a particular branch within a family or family within a clan. The term has also taken on other contemporary meanings.