a republic in SW Arabia, on the Red Sea and the Gulf of Aden; formed in 1990 from the union of North Yemen and South Yemen; civil war since 2014 when Houthi rebels overran the capital; consists of arid coastal lowlands, rising to fertile upland valleys and mountains in the west and to the Hadhramaut plateau in the SE; the north and east contains part of the Great Sandy Desert. Official language: Arabic. Official religion: Muslim. Currency: riyal. Capital: San'a. Pop: 28 250 420 (2017 est). Area (including territory claimed by Yemen along the undemarcated eastern border with Saudi Arabia): 472 099 sq km (182 278 sq miles)