Sand and dunes of the Libyan desert

Valle de la Luna ("Valley of the Moon") in the Atacama Desert of Chile, the world's driest desert.

A desert is an arid (dry) biome. They get less than 25 cm (9.8 inches) of rainfall a year. It is "any region that can have a moisture deficit over the course of a year". In other words, they can have less rainfall in a year than they give up through evaporation".