a sultanate in NW Borneo, consisting of two separate areas on the South China Sea, otherwise bounded by Sarawak: controlled all of Borneo and parts of the Philippines and the Sulu Islands in the 16th century; under British protection since 1888; internally self-governing since 1971; became fully independent in 1984 as a member of the Commonwealth. The economy depends chiefly on oil and natural gas. Official language: Malay; English is also widely spoken. Religion: Muslim. Currency: Brunei dollar. Capital: Bandar Seri Begawan. Pop: 428 697 (2017 est). Area: 5765 sq km (2226 sq miles)