country in east central Europe bordering on the Baltic Sea; in the medieval period a kingdom, at one time extending to the lower Dnieper; partitioned 1772, 1793, and 1795 among Russia, Prussia, and Austria; again a kingdom 1815–30; lost autonomy 1830–1918; since 1918 a republic; capital Warsaw area 120,728 square miles (312,685 square kilometers), population 38,421,000