Within each of the four major hierarchical Varnas of the Caste System there exist, in fact if not in theory, numerous caste groups. The Imperial Gazetteer provides a careful list of the most important castes throughout British India. Each of these castes was usually also internally divided into various sub-castes. The Imperial Gazetteer, in its discussion of castes, gives a number of mechanisms by which such sub-castes might form. Like castes (only usually less radically, since there was usually less social distance involved), sub-castes had complex rules and practices among themselves to regulate interdining and, above all, intermarriage.
Annotation by: Pritchett