A group of soils in the broadest category. For example, in the 1938 classification system. The three soil orders were zonal soil, intrazonal soil, and azonal soil. In the 1975 there were 10 orders, whereas in the current USDA classification scheme (Soil Survey Staff. 1994. Soil taxonomy: A basic system of soil classification for making and interpreting soil surveys. SCS-USDA. U. S. Gov. Print. Office, Washington, DC) there are 11 orders, differentiated by the presence or absence of diagnostic horizons: Alfisols, Andisols, Aridisols, Entisols, Histosols, Inceptisols, Mollisols, Oxisols, Spodosols, Ultisols, Vertisols. Orders are divided into Suborders and the Suborders are farther divided into Great Groups.