Dollar is the monetary unit of the United States, Canada, and many other countries. The dollars of the United States and Canada are paper bills or coins equal to 100 cents. The U.S. dollar was modeled after a Spanish coin called the peso or piece of eight. The origin of the dollar sign ($) is unknown. It probably developed from ps, an abbreviation of the word peso. The use of the dollar sign has become as widespread as the use of the currency it represents.