The Amazon River (US /ˈæməzɒn/ or UK /ˈæməzən/; Spanish and Portuguese: Amazonas) in South America is generally regarded as the second longest river in the world and is by far the largest by waterflow with an average discharge of about 209,000 cubic meters per second (7,381,000 cu ft/s), greater than the next seven largest rivers combined (not including Madeira and Rio Negro, which are tributaries of the Amazon). The Amazon, which has the largest drainage basin in the world, about 7,050,000 square kilometres (2,720,000 sq mi), accounts for approximately one-fifth of the world’s total river flow. The river would have the biggest drainage basin in the world even just counting Brazil, which it enters with only one-fifth of the volume that will finally be discharged into the Atlantic.
In its upper stretches, above the confluence of the Rio Negro, the Amazon is called Solimões in Brazil; however, in Peru, Colombia and Ecuador, as well as the rest of the Spanish-speaking world, the river is generally called the Amazon downstream from the confluence of the Marañón and Ucayali rivers in Peru. The Ucayali-Apurímac river system is considered the main source of the Amazon, with its main headstream being the Carhuasanta glacial stream flowing off the Nevado Mismi mountain.
The width of the Amazon is between 1.6 and 10 kilometres (1.0 and 6.2 mi) at low stage but expands during the wet season to 48 kilometres (30 mi) or more. The river enters the Atlantic Ocean in a broad estuary about 240 kilometres (150 mi) wide. The mouth of the main stem is 80 kilometres (50 mi). Because of its vast dimensions, it is sometimes called The River Sea. The first bridge in the Amazon river system (over the Rio Negro) opened on 10 October 2010 near Manaus, Brazil.
The total volume of water of the Amazon river in a year is about 6,591 cubic kilometers (to compare, the water volume of Lake Baikal is 23,615 cubic km).