A desert is a barren aurie o land whaur little precipitation occurs an consequently livin condeetions are hostile for plant an animal life. The lack o vegetation expones the unpertectit surface o the grund tae the processes o denudation. Aboot ane third o the land surface o the warld is arid or semi-arid. This includes much o the polar regions wheaur little precipitation occurs an which are sometimes cried "cold deserts". Thare are a nummer o ways o classifyin deserts includin bi the amoont o precipitation that faws, bi the temperatur that prevails, bi the causes o desertification or bi the geografical location o the desert.