Definition of Caste. A caste is a social category to which a person belongs involuntarily (one's social status is ascribed); a caste contrasts with a social class. A caste system, then, is a social structure in which people belong to such social categories; historically, an example is the caste system of India.In sociology, a caste system describes one form of social stratification.astes also explain why some societies offer little social mobility: if a person occupies a low social status in that person's caste, then it is difficult or impossible for that person to achieve a higher status, as typically one cannot change one's caste.