currency - the metal or paper medium of exchange that is presently used

fractional currency - paper currency in denominations less than the basic monetary unit

fiat money - money that the government declares to be legal tender although it cannot be converted into standard specie

bank bill, bank note, banker's bill, banknote, Federal Reserve note, government note, greenback, bill, note - a piece of paper money (especially one issued by a central bank); "he peeled off five one-thousand-zloty notes"