Orange Longest river of South Africa. It rises in the Drakensberg Mountains in n Lesotho and flows generally w, forming the boundary between Free State and Cape Province. It continues w through the Kalahari and Namib deserts, forming South Africa's border with Namibia. It empties into the Atlantic Ocean at Oranjemund. Length: c.1300mi (2100km).

orange Evergreen citrus tree and its fruit. There are two basic types. The sweet orange (Citrus sinensis) is native to Asia and widely grown in the USA and Israel. The fruit develops without flower pollination and is often seedless. The sour orange (C. aurantium) is widely grown in Spain for the manufacture of marmalade. Related fruits include the mandarin, tangerine, and satsuma – all varieties of C. reticulata. Height: to 9m (30ft). Family Rutaceae; genus Citrus.