<Tr> <Td> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> A currency (from Middle English: curraunt, "in circulation", from Latin: currens, - entis), 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 stores of value and are traded between nations in foreign exchange markets, which determine the relative values of the different currencies . Currencies in this sense are defined by governments, and each type has limited boundaries of acceptance . </P> <P> Other definitions of the term "currency" are discussed in their respective synonymous articles banknote, coin, and money . The latter definition, pertaining to the currency systems of nations, is the topic of this article . Currencies can be classified into two monetary systems: fiat money and commodity money, depending on what guarantees the value (the economy at large vs. the government's physical metal reserves). Some currencies are legal tender in certain political jurisdictions . Others are simply traded for their economic value . Digital currency has arisen with the popularity of computers and the Internet . </P>

Which words refers to any system that uses an exchange medium