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
Currency substitution may reduce the possibility of systematic liquidity shortages and the optimal reserves in the banking system. Research has shown that official currency substitution has played a significant role in improving bank liquidity and asset quality in Ecuador and El Salvador. High and unanticipated inflation rates decrease the demand for domestic money and raise the demand for alternative assets, including foreign currency and assets dominated by foreign currency. This phenomenon is called the "flight from domestic money". It results in a rapid and sizable process of currency substitution. In countries with high inflation rates, the domestic currency tends to be gradually