Urban Agglomeration UPSC relevant
An urban agglomeration (UA) is 'a continuous urban spread constituting a town and its adjoining outgrowths, or two or more physically contiguous towns together with or without outgrowths of such towns.' Since 2001 a UA must contain at least one statutory town, and its total population (all constituents combined) must be at least 20,000.
Outgrowths are urbanised areas — railway colonies, university campuses, port areas — adjoining a town but outside its statutory limits. UAs are how the census measures real city size across municipal boundaries: 'Greater Mumbai UA' or 'Delhi UA' figures are UA populations, not municipal ones. Census 2027 will re-delineate UAs on the boundaries frozen January 1, 2026, producing the first official update of India's city-size hierarchy since 2011.