A metropolitan area, sometimes referred to as a metro area or commuter belt, is a region consisting of a densely populated urban core and its less-populated surrounding territories, sharing industry, infrastructure, and housing. A metro area usually comprises multiple jurisdictions and municipalities: neighborhoods, townships, boroughs, cities, towns, exurbs, suburbs, counties, districts, states, and even nations like the eurodistricts. As social, economic and political institutions have changed, metropolitan areas have become key economic and political regions. Metropolitan areas include one or more urban areas, as well as satellite cities, towns and intervening rural areas that are socioeconomically tied to the urban core, typically measured by commutingpatterns. In the United States, the concept of the metropolitan statistical area has gained prominence.
For urban centres outside metropolitan areas, that generate a similar attraction at smaller scale for their region, the concept of the regiopolis and respectively regiopolitan area or regio was introduced by German professors in 2006. In the United States, the term micropolitan statistical area is used.