A dollar is a unit of currency used in several countries, most notably in the United States. It is represented by the symbol "$" and is divided into 100 smaller units called cents. The dollar is commonly used for everyday transactions, such as buying goods and services. In the U.S., the dollar comes in both paper and coin forms. Paper dollars are available in denominations of $1, $5, $10, $20, $50, and $100. Coins include the penny (1 cent), nickel (5 cents), dime (10 cents), quarter (25 cents), and half dollar (50 cents). The dollar plays a crucial role in the global economy.