Somalia,[a] officially the Federal Republic of Somalia, is a country in the Horn of Africa. It is bordered by Ethiopia to the west, Djibouti[12] to the Northwest, the Gulf of Aden to the north, the Indian Ocean to the east, and Kenya to the southwest. Somalia has the longest coastline on Africa's mainland.[13] Its terrain consists mainly of plateaus, plains, and highlands.[2] Hot conditions prevail year-round, with periodic monsoon winds and irregular rainfall.[14] Somalia has an estimated population of around 15 million[15][16], of which over 2 million live in the capital and largest city Mogadishu, and has been described as Africa's most culturally homogeneous country.[17][18] Around 85% of its residents are ethnic Somalis,[2] who have historically inhabited the country's north. Ethnic minorities are largely concentrated in the south.[19] The official languages of Somalia are Somali and Arabic.[2] Most people in the country are Muslims,[20] the majority of them Sunni.[21]