RhymeZone: koppa definitions

Definitions of Koppa:

noun: The 18th Ancient Greek letter in early versions of the Greek alphabet, Ϙ (lowercase ϙ).
noun: The Greek numeral Ϟ (lowercase ϟ), descended from the ancient letter and having the numerical value of 90.
noun: The archaic Cyrillic numeral Ҁ (lowercase ҁ), descended from the ancient Greek letter and having the numerical value of 90.

(Definitions from Wiktionary)