"What is the class system"@en . . . "The class system or social class is a set of concepts in the social sciences and political theory centered on models of social stratification in which people are grouped into a set of hierarchical social categories, the most common being the upper, middle, and lower classes."@en . "The class system or social class is a set of concepts in the social sciences and political theory centered on models of social stratification in which people are grouped into a set of hierarchical social categories, the most common being the upper, middle, and lower classes."@en .