The Sudd (a s-Sudd or al-Sudd) is a vast swamp in South Sudan, formed by the White Nile's Baḥr al-Jabal section. The Arabic word sudd is derived from sadd (سد), meaning "barrier" or "obstruction". The term "the sudd" has come to refer to any large solid floating vegetation island or mat. The area which the swamp covers is one of the world's largest wetlands and the largest freshwater wetland in the Nile basin.