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
Shadi A. Karam reasons for this are "principally the lack of extensive distribution networks, the absence of comprehensive trade agreements that go beyond the existing accords and the fact that transactions have to go through the US dollar." As such, Karam has become one of the leading voices in the Arab Middle East calling for a common currency. "The pegging to the US dollar of most of the major currencies in the region will facilitate the technical engineering of the process," he says. "This currency could be named the Umma, with reference to the unattainable dream of a unified Arab nation." Admitting that