a river in Yugoslavia, a right tributary of the Sava River of the Danube River basin. The Una is 214 km long and drains an area of about 7,500 sq km. It rises in the Dinaric Mountains and for most of its length flows through the Dinaric Alps in a deep valley, forming numerous rapids. High water occurs in the spring; in the autumn, freshets result from rains. The mean flow rate near the river’s mouth is about 200 cu m per sec. The cities of Bihac, Bosanski Novi, Dvor, and Bosanska Dubica are located on the Una. In its lower course the river is navigable by small craft.