TEREK, a river of Russian Caucasia. It rises in the Caucasus, on the slopes of Mount Kasbek, in several head-streams, and flows north as far as Vladikavkaz, just above which it emerges from the mountains, Then it flows N.W. and N. as far as approximately 43° 45' N., whereupon it swings round to the E. and pursues that direction as far as 46° 30' E. Finally, after a comparatively short run towards the N.N.E., it branches out into a large delta on the west side of the Caspian Sea. This river, the ancient Alutas, is at first an impetuous mountain torrent, as are also all its chief tributaries—the Zunzha on the right, and the Ardon, Urukh, Cherek, Urvan, Chegem, Baksan and Malka on the left. All these streams, except the first-named, rise at altitudes of 8000 to 9000 ft. between Mount Kasbek and Mount Elbruz. In its lower course the Terek becomes very sinuous and sluggish, and frequently overflows its banks with disastrous results. Opposite its mouth it forms large sand-banks in the Caspian, and is nowhere navigable. Its length is 300 m., and the area of its drainage basin extends to 22,800 sq. m.