noun, Pathology. 1. the accumulation of excessive ketones in the body, as in diabetic acidosis. Origin of ketosis. 1915-1920.
Climate zones of Africa, showing the ecological break between the hot desert climate of the Sahara Desert (red), the hot semi-arid climate of the Sahel (orange) and the tropical climate of Central and Western Africa (blue).
The Sahara Desert is considered one of the harshest climates on the planet, due to its variable high temperatures during the day and the rapid and sometimes significant cooling in the night. The Sahara is the largest desert on the planet. The existing arid state of the Sahara has been a feature of the desert since approximately 3000 B.C.E.