​ZONE (Gr. ζώνη a girdle, from ζωννύναι, to gird), a term for a belt or girdle, now used chiefly in the transferred sense of a demarcated area. Thus the earth’s surface is divided, for classification of climates, into five climatic zones: the two temperate and the two frigid zones and the tropical or torrid zone. (See Climate and Climatology.)