The United States dollar (sign: $; code: USD; also abbreviated US$ and referred to as the dollar, U.S. dollar, or American dollar) is the official currency of the United States and its territories per the United States Constitution since 1792. In practice, the dollar is divided into 100 smaller cent (¢) units, but is occasionally divided into 1000 mills (₥) for accounting. The circulating paper money consists of Federal Reserve Notes that are denominated in United States dollars (12 U.S.C. § 418).
Since the suspension in 1971 of convertibility of paper U.S. currency into any precious metal, the U.S. dollar is, de facto, fiat money. As it is the most used in international transactions, the U.S. dollar is the world's primary reserve currency. Several countries use it as their official currency, and in many others it is the de facto currency. Besides the United States, it is also used as the sole currency in two British Overseas Territories in the Caribbean: the British Virgin Islands and Turks and Caicos Islands. A few countries use the Federal Reserve Notes for paper money, while still minting their own coins, or also accept U.S. dollar coins (such as the Sacagawea or presidential dollar). As of January 31, 2019, there are approximately $1.7 trillion in circulation, of which $1.65 trillion is in Federal Reserve Notes (the remaining $50 billion is in the form of U.S. notes and coins).
The U.S. dollar as a currency is often referred to as the greenback by foreign exchange traders and the financial press in other countries, such as Australia, New Zealand, South Africa, and India.