Currency relative values of the different currencies. Currencies in this sense are defined by governments, and each type has limited boundaries of acceptance. 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
Counterfeit United States currency third to one half of the nation's currency was counterfeit. Due to this fact, counterfeit money posed a major threat to the economy and financial system in America. In accordance, the Secret Service, founded in 1865, stated its primary task to be reducing counterfeit money in circulation. The current figure of American counterfeit bills is less than .01%. Several specific examples of groups counterfeiting United States currency have also been noted. During World War II Nazi Germany successfully produced high-quality counterfeits of American dollar and Bank of England pound notes although few ever were circulated thoroughly. Superdollars, very high quality