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 metro area usually comprises multiple principal cities, jurisdictions and municipalities: neighborhoods, townships, boroughs, cities, towns, exurbs, suburbs, counties, districts, and even states and nations like the eurodistricts. As social, economic and political institutions have changed, metropolitan areas have become key economic and political regions.
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Metropolitan areas include satellite cities, towns and intervening rural areas that are socioeconomically tied to the principal cities or urban core, typically measured by commuting patterns. Some metropolitan areas are anchored by one core city such as Paris metropolitan area (Paris), Mumbai Metropolitan Region (Mumbai (Bombay). In many cases metropolitan areas have multiple centers of close to equal importance, such as Dallas–Fort Worth metropolitan area (Dallas and Fort Worth), Islamabad–Rawalpindi metropolitan area (Islamabad and Rawalpindi), the Rhine-Ruhr in Germany and the Randstad in the Netherlands.
In the United States, the concept of the metropolitan statistical area has gained prominence. The area of Greater Washington Washington metropolitan area is an example of statistically grouping independent cities and county areas from various states to form a larger city ( The United Nations Top eighty worldwide List of largest cities) because of proximity, history and recent urban convergence. Metropolitan areas may themselves be part of larger megalopolises. 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.