ZVORNIK, SWORNIK, or ISVORNIK, a town of European Turkey, province of Bosnia, on the left bank of the Drina, 45 miles N.E. of Bozna-Serai. It is strongly fortified, being surrounded by walls, and further defended by a castle on a steep hill above the town. It has mosques, and Greek and Roman Catholic churches, and carries on a considerable trade with Belgrade, Semlin, &c., especially in
timber and fuel. There are some lead-mines in the vicinity. Pop. about 14,000.