Sahel Africa is a wide stretch of land running from the Atlantic ocean to the African "Horn", an area that contains the countries of Ethiopia, Eritrea, Djibouti, and Somalia. The name Sahel accurately describes where this area is located because it is an Arabic word for "border" or "margin". The southern border of the region is the Sahara Dessert (Sahara being an Arabic word for "desert"). It is a transition zone between the arid Sahara to the north and the wetter more tropical area to the south. The areas primarily affected are: Senegal, Mauritania, Mali, Burkina Faso, Niger, Nigeria, Chad, Sudan, and the "Horn."