A cognomen (/kɒɡˈnoʊmən/;[1][2] Classical Latin: [koːŋˈnoːmen]; Latin plural cognomina; from 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 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.