A flat, largely waterless, sparsely populated, and sand-covered region in south-central Africa which occupies much of Botswana, plus adjacent parts of South Africa and Namibia. The precise boundaries of the Kalahari are difficult to define since it merges into humid regions to the north and east, and the arid Karoo and Namib further south and west. However, the generally agreed-upon boundaries are the Okavango-Zambezi “swamp zone” in the north and the Orange River in the south, with the western and eastern boundaries (in eastern Namibia and eastern Botswana, respectively) coinciding with the extent of the sandy Kalahari group sediments (see illustration).