Currency Currency A currency (from , "in circulation", from ), in the most specific use of the word, refers to money in any form when in actual use or circulation as a medium of exchange, especially circulating banknotes and coins. A more general definition is that a currency is a "system of money" (monetary units) in common use, especially in a nation. Under this definition, US dollars, British pounds, Australian dollars, European euros and Russian ruble are examples of currency. These various currencies are recognized as stores of value and are traded between nations in foreign exchange markets, which determine the
Currency mostly paper, but Australia's Commonwealth Scientific and Industrial Research Organisation developed the world's first polymer currency in the 1980s that went into circulation on the nation's bicentenary in 1988. Now used in some 22 countries (over 40 if counting commemorative issues), polymer currency dramatically improves the life span of banknotes and prevents counterfeiting. Currency use is based on the concept of lex monetae; that a sovereign state decides which currency it shall use. Currently, the International Organization for Standardization has introduced a three-letter system of codes (ISO 4217) to define currency (as opposed to simple names or currency signs), in