Currency
Currency is a unit of money that facilitates the purchase of goods or services. Each modern nation has one currency, such as the U.S. dollar in the United States, the pound sterling in The United Kingdom, and the Euro in several countries across Europe.
More specifically, currency is something (as coins, treasury notes, and banknotes) that is in circulation as a medium of exchange, paper money in circulation, or a common article for bartering. [1]
The invention of currency allowed civilization to advance beyond the barter system.
=Currency in the United States
The denominations of currency produced in the United States are $1, $2, $5, $10, $20, $50, and $100. Larger denominations used be produced, including a $100,000 bill, featuring a portrait of Woodrow Wilson, that was produced at one time. In 1969, President Richard Nixon issued an executive order withdrawing bills larger than $100 from circulation "to make life harder for the mafia". [2]