Episemon

Episēmon (Greek ἐπίσημον, from epi- "on" plus sēma "sign"; plural: episēma) is a Greek word that can mean:

• a distinguishing mark or symbol, also called parasēmon, especially in the following contexts:
  • an ensign or figurehead on an ancient ship
  • a characteristic symbol displayed on a shield, similar to a coat of arms
  • a characteristic symbol stamped on an ancient coin

• another name for the Greek letter Digamma, the numeral sign for "6"
• a generic term for all three Greek numeral signs (Digamma 6, Koppa 90, and Sampi 900) in the system of Greek numerals, or similar symbols in other scripts