Institutionalized systems that rank people into unequal social strata with unequal access to wealth, power or status, including caste systems, patriarchy and matriarchy as gendered stratification, meritocracy as an ideology of stratification by achievement, serfdom and slavery as coerced-labor stratification, and social class stratification generally. Belongs here: any named system that institutionally sorts a population into unequal ranked strata. Does not belong here: the formal governing apparatus that a stratification system may rely on for enforcement, grouped under Political and Legal Institutions.