Desert, an arid region with little or no vegetation. The word comes from a Latin word meaning abandoned or forsaken, signifying lack of human habitation. Although deserts seem to be uninhabited, some kinds of plants and animals have adapted to the harsh conditions. People, too, live in or near deserts—traditionally as oasis dwellers or nomads. In the 20th century, permanent settlement in some deserts has increased, largely due to improved means of obtaining water and to such inventions as air conditioning.

The term desert usually refers to areas that, in addition to being extremely dry, have high daytime temperatures, particularly in the summer. Many scientists also consider polar regions to be deserts, since they are arid and sustain little or no vegetation.

For information on polar areas, the discussion in this article is concerned with deserts in the usual sense.

Deserts occupy between 15 and 20 per cent of the earth's land area. They usually receive less than 10 inches (250 mm) of precipitation yearly. Precipitation, usually rain, tends to come in a few heavy storms of short duration. Deserts are often bordered by semiarid areas.