1) International river of Asia 2) River in Iran 3) Tributary of the Caspian Sea 
(from the article `Turkmenistan`) Turkmenistan`s main rivers are the Amu Darya (ancient Oxus River), which flows along its northeastern border toward the Aral Sea, and the Tejen, ...
a river arising in NE Iran, flowing W, then along the Iran-Turkmenistan border, and through Turkmenistan into the Caspian Sea. ab. 300 mi. (485 km) long.