A megalopolis or a supercity, also called a megaregion, is a group of metropolitan areas which are perceived as a continuous urban area through common systems of transport, economy, resources, ecology, and so on. They are integrated enough that coordinating policy is valuable, although the constituent metropolises keep their individual identities. The megalopolis concept has become highly influential as it introduced a new, larger scale thinking about urban patterns and growth.

A metropolitan area or metro is a region consisting of a densely populated urban agglomeration and its surrounding territories sharing industries, commercial areas, transport network, infrastructures and housing. A metropolitan area usually comprises multiple principal cities, jurisdictions and municipalities: neighborhoods, townships, boroughs, cities, towns, exurbs, suburbs, counties, districts and even states and nations in areas like the eurodistricts. As social, economic and political institutions have changed, metropolitan areas have become key economic and political regions.