Persian: آمودریا, translit. Âmudaryâ; Turkmen: Amyderýa/Амыдеря; Uzbek: Amudaryo/Амударё/ەمۇدەريا; Tajik: Амударё, Amudaryo; Pashto: د آمو سيند, də Āmú Sínd; Turkish: Ceyhun, Amu Derya; Ancient Greek: Ὦξος, translit. Ôxos). In classical antiquity, the river was known as the Ōxus in Latin and Ὦξος (Ôxos) in Greek — a clear derivative of Vakhsh, the name of the largest tributary of the river. In Vedic Sanskrit, the river is also referred to as Vakṣu (वक्षु). The Brahmanda Purana refers to the river as Chaksu. The Avestan texts too refer to the River as Yakhsha/Vakhsha (and Yakhsha Arta ("upper Yakhsha") referring to the Jaxartes/Syr Darya twin river to Amu Darya). In Middle Persian sources of the Sassanid period the river is known as Wehrōd (lit. "good river").
The name Amu is said to have come from the medieval city of Āmul, (later, Chahar Joy/Charjunow, and now known as Türkmenabat), in modern Turkmenistan, with Darya being the Persian word for "river". Medieval Arabic and Islamic sources call the river Jayhoun (Arabic: جَـيْـحُـوْن, translit. Jayḥūn; also Jaihun, Jayhoon, or Dzhaykhun) which is derived from Gihon, the biblical name for one of the four rivers of the Garden of Eden.
Western travelers in the 19th century mentioned that one of the names by which the river was known in Afghanistan was Gozan, and that this name was used by Greek, Mongol, Chinese, Persian, Jewish, and Afghan historians. However, this name is no longer used.
The river's total length is 2,400 kilometres (1,500 mi) and its drainage basin totals 534,739 square kilometres (206,464 sq mi) in area, providing a mean discharge of around 97.4 cubic kilometres (23.4 cu mi) of water per year. The river is navigable for over 1,450 kilometres (900 mi). All of the water comes from the high mountains in the south where annual precipitation can be over 1,000 mm (39 in). Even before large-scale irrigation began, high summer evaporation meant that not all of this discharge reached the Aral Sea – though there is some evidence the large Pamir glaciers provided enough melt water for the Aral to overflow during the 13th and 14th centuries.
Since the end of the 19th century there have been four different claimants as the true source of the Oxus: