an ancient region in southern Mesopotamia that contained a number of independent cities and city-states of which the first were established possibly as early as 5000 b.c.: conquered by the Elamites and, about 2000 b.c., by the Babylonians; a number of its cities, as Ur, Uruk, Kish, and Lagash, are major archaeological sites in southern Iraq.
Su·mer (sōō'mər) An ancient country of southern Mesopotamia in present-day southern Iraq. Archaeological evidence dates the beginnings of Sumer to the fifth millennium B.C. By 3000 a flourishing civilization existed, which gradually exerted power over the surrounding area and culminated in the Akkadian dynasty, founded c. 2340 by Sargon I. Sumer declined after 2000 and was later absorbed by Babylonia and Assyria. The Sumerians are believed to have invented the cuneiform system of writing.
[soo-mer] 
mər