Short answers, pulled from the story.
The Amazon River is the largest river by discharge volume of water in the world. Its average discharge is greater than the next seven largest independent rivers combined, and two of the top ten rivers by discharge are its tributaries. It represents about 20 percent of the global riverine discharge into the oceans.
A 2014 study by James Contos and Nicolas Tripcevich identified the most distant source of the Amazon in the Rio Mantaro drainage at the Cordillera Rumi Cruz in Peru. For nearly a century before that, the source was thought to be the Apurimac River headwaters on Nevado Mismi, a peak 5597 m high. The 2014 finding moved the source nearly 80 km farther upstream.
Whether the Amazon or the Nile is the longest river has been disputed for many years. The Amazon has been reported between 6275 km and 6992 km long, and the Nile between 5499 and 7088 km. A 2009 peer-reviewed article concluded the Nile is longer, while a 2008 Brazilian study claimed the Amazon was 140 km longer. The Encyclopaedia Britannica holds the final length remains open to interpretation.
For millions of years the Amazon flowed from east to west toward the Pacific Ocean. The main tectonic uplift of the Andes, beginning about fifteen million years ago and caused by the Nazca Plate subducting beneath the South American Plate, blocked that flow. The river reversed toward its current mouth in the Atlantic, and took its present shape about 2.4 million years ago.
The Amazon was named after native warriors, led by women, who attacked Francisco de Orellana's 16th-century expedition and reminded him of the Amazon warriors of Greek mythology. The word Amazon may derive from an Iranian compound meaning one fighting together or warriors. Europeans first knew the river as the Maranon.
There are no bridges across the entire width of the Amazon River, not because it is too wide to bridge, but because for most of its course it flows through the Amazon Rainforest where there are very few roads and cities. Crossings are usually made by ferry. The Manaus Iranduba Bridge spans only the Rio Negro, a tributary, just before its confluence.
The Amazon River is home to more than 5,600 known fish species, with roughly fifty new species discovered each year. Notable inhabitants include the boto or Amazon river dolphin, which turns from gray to pink to white as it ages, the arapaima which reaches up to 15 ft, the giant otter, anacondas, piranhas, electric eels, and bull sharks reported 4000 km upriver at Iquitos.
The Amazon River, a lifeline for more than 47 million people, faces drought, illegal gold mining, and damming. In 2022 severe drought pushed water temperatures to 39.1 degrees Celsius and killed 125 river dolphins, and the river has hit its lowest levels in over a century. Around 412 dams operate on its tributaries, with hundreds more planned.