Currency is the paper and coin money that a country uses to conduct business. The United States uses a currency that's made up of dollars, quarters, nickels, dimes, and pennies.
Just about every country has its own currency — the money its people use to pay for their groceries, clothes, and other goods. Paper currency in the United States is all green and can confuse people who use bills with different colors for different denominations. In addition to describing a country's monetary system, currency means something that is accepted or used. The slang word "daddy-o" was the currency in the 1950s, but people who say it today can expect to receive strange looks.