Semi-Arid is a category of dryland characterized by very little annual rainfall, usually from 10 to 20 in. (25 to 50 cm).

Origin of this word is traced back to 1895–1900.

A more precise definition is given by the Köppen climate classification that treats steppe climates (BS) as intermediates between the desert climates (BW) and humid climates in ecological characteristics and agricultural potential. The Köppen climate classification allows adjustments for temperature and for excluding forested regions (such as those in most of Canada and Siberia).