Currency

Currency (also known as money) refers to a standardized medium of exchange for trade. Currency evolved along with civilization, starting from simple barter and moving towards systems of currency based around masses of certain rare metallic elements such as gold and silver. In the modern world, most currencies are backed by the legal authority of the issuing government on the matter of transactions.

Currency in Science Fiction and Fantasy

• In the Star Trek, the United Federation of Planets has abolished currency, although other governments such as the Klingon Empire still issue currencies. An analog to the Gold Standard is used by the Ferengi -- and honored by others powers -- based around "gold-pressed latinum."
• In Star Wars, the standard unit of currency is the "credit". The earliest mention of credits was Qui-Gon Jinn's failed attempt to purchase a hyperdrive with "Republic Daktaris"; these "Republic credits" were not valued on Tatooine at the time. Presumably these credits are issued and backed by the Republic and, later, the Empire.
• In Stargate, Naquadah is often used as currency.
• In the Terry Pratchett Discworld novel Making Money, the plot focuses around the nature of money and the introduction of banknotes.