A metropolis  is a large city or conurbation which is a significant economic, political, and cultural center for a country or region, and an important hub for regional or international connections, commerce, and communications. The term is Ancient Greek (?) and means the "mother city" of a colony (in the ancient sense), that is, the city which sent out settlers. This was later generalized to a city regarded as a center of a specified activity, or any large, important city in a nation.
A big city belonging to a larger urban agglomeration, but which is not the core of that agglomeration, is not generally considered a metropolis but a part of it. The plural of the word is metropolises, although the Latin plural is metropoles, from the Greek metropoleis (?o).
For urban centers outside metropolitan areas that generate a similar attraction at smaller scale for their region, the concept of the regiopolis ("regio" for short) was introduced by German academics in 2006.
In the ancient world, a metropolis was the city or state of origin of a colony.
Metropolis (?) is a Greek word, coming from , m?t?r meaning "mother" and , pólis meaning "city" or "town", which is how the Greek colonies of antiquity referred to their original cities, with whom they retained cultic and political-cultural connections. The word was used in post-classical Latin for the chief city of a province, the seat of the government and, in particular, ecclesiastically for the seat or see of a metropolitan bishop to whom suffragan bishops were responsible. This usage equates the province with the diocese or episcopal see.
The concept of a global city (or world city) is of a city that has a direct and tangible effect on global affairs through socioeconomic means. The term has become increasingly familiar, because of the rise of globalization (i.e., global finance, communications, and travel). An attempt to define and categorize world cities by financial criteria was made by the Globalization and World Cities Research Network (GaWC), based primarily at Loughborough University in England. The study ranked cities based on their provision of "advanced producer services" such as accountancy, advertising, finance and law. The inventory identifies three levels of world cities and several sub-ranks (see GaWC study).
A metropolis is not necessarily a global city--or, being one, it might not be among the top-ranking--due to its standards of living, development, and infrastructure. A metropolis that is also a global city is a global metropolis.
Lagos is the most populous metropolis in Nigeria as well as in Africa.
In South Africa, a metropolitan municipality or "Category A municipality" is a municipality which executes all the functions of local government for a conurbation. This is by contrast to areas which are primarily rural, where the local government is divided into district municipalities (comparable to a "county" in the US) and local municipalities. There are eight metropolitan municipalities in South Africa.
In Argentina, Buenos Aires is the principal metropolis with a population of around fifteen and a half million.The Greater Buenos Aires conurbation, which also includes several Buenos Aires Province districts, constitutes the third-largest conurbation in Latin America. Buenos Aires is the main political, financial, industrial, commercial, and cultural hub of Argentina.
In Brazil, São Paulo is the principal metropolis with over 20 million inhabitants. In the larger cities, such as São Paulo and Rio de Janeiro (population 6.3 million), favelas (slums) grew up over decades as people migrated from rural areas in order to find work. The term used in Brazilian Portuguese for a metropolitan area is Região Metropolitana. Others metropoles in Brazil with more than one million inhabitants include: Belém, Belo Horizonte, Brasília, Campinas, Curitiba, Feira de Santana, Fortaleza, Goiânia, Manaus, Porto Alegre, Recife, and Salvador.
The City of Toronto has a population of 3 million while The Greater Toronto Area is Canada's most urbanized region with a population of over 10 million people. Statistics Canada defines a census metropolitan area as one or more adjacent municipalities situated around a major urban core where the urban core has a population of at least 100,000. Canada's largest metropoles are Toronto, Ontario, Montreal, Quebec and Vancouver, British Columbia.
The primary metropolis in Chile is Santiago, with a population of 7 million in the metropolitan area. Santiago is the main political, financial, industrial, commercial, and cultural hub of Chile.
In Colombia, Bogotá is the main metropolis with over 13 million inhabitants residing in its Metropolitan Area, which includes boroughs like Soacha, Mosquera, Cota, and Chía. The second metropolis in Colombia is Medellín, which includes such boroughs as Envigado, Itagüi, La Estrella, and Sabaneta. This metropolitan area is known for having the first and only Metro in Colombia, the Medellín Metro. Bogotá has the Transmilenio, a Rapid Transit Metro-bus system.
In Mexico, the term metropolis is used to refer to an urban area of economic, political, and cultural importance. Mexico City represents all three factors as it is the country's capital and financial center. Other metropolis are Monterrey and Guadalajara, both metropolitan areas with a population over 4,000,000 inhabitants.
The Lima metropolitan area is Peru's capital and largest city with over 10 million inhabitants, more than one third of the total national population.
In the United States, an incorporated area or group of areas having a population more than 50,000 is required to have a metropolitan planning organization in order to facilitate major infrastructure projects and to ensure financial solvency. Thus, a population of 50,000 or greater has been used as a de facto standard to define a metropolis in the United States. A similar definition is used by the United States Census Bureau. The bureau defines a metropolitan statistical area as "at least one urbanized area of 50,000 or more inhabitants." The ten largest metropolitan cities in the USA are New York City, Los Angeles, Chicago, Dallas, Houston, Philadelphia, Washington, Miami, Atlanta, and Boston, with New York City being the largest.
In the People's Republic of Bangladesh, there are eleven metropolitan areas: Dhaka North, Dhaka South, Gazipur, Chittagong, Rajshahi, Khulna, Sylhet, Barisal, and Rangpur. Lands are highly priced and residents are considered to have a better urban lifestyle. Special police departments are allotted for the metropolitan cities, and there are city corporations for which mayors are elected for five-year regimes. Most of these cities have population density of 35,000/square mile or more. Dhaka is considered a mega city because its population surpasses 10 million.
As of the 2011 Indian census, there are 53 urban agglomerations with a population of one million or more. The top-ten metropolitan areas based on their population are Mumbai, Delhi, Kolkata, Chennai, Bangalore, Visakhapatnam, Kochi , Hyderabad, Ahmedabad, Pune, Surat, Mysore and Jaipur. Other important cities include Nagpur, Lucknow etc. The Census Commission defines the qualification for metropolitan city as, "the cities having a population of more than 10 lakhs (one million) and above" and Megacity as, "the cities having a population of more than 10 million and above".
In Indonesia, the metropolitan cities are in Jabodetabek (Jakarta, Bogor, Depok, Tangerang, Bekasi), the biggest metropolitan area in Southeast Asia and the fifth metropolitan area in the world (2007). The other cities are Surabaya, Bandung, Semarang and Medan.
The Japanese legal term to (?) is by designation to be translated as "metropolis". however existing translations predate the designation. Structured like a prefecture instead of a normal city, there is only one to in Japan, namely Tokyo. As of 2008 , Japan has 11 other cities with populations greater than one million. The same Kanji character in Chinese, or in generic Japanese (traditional or non-specific), translates variously--city, municipality, special municipality--all qualify.
Metropolitan Manila, or Metro Manila, is the metropolitan region encompassing the city of Manila and its surrounding areas in the Philippines. It is composed of 17 cities namely Manila, Caloocan, Las Piñas, Makati, Malabon, Mandaluyong, Marikina, Muntinlupa, Navotas, Pasay, Pasig, Parañaque, Quezon City, San Juan, Taguig, Valenzuela and Pateros. The region is the political, economic, social, cultural, and educational center of the Philippines. As proclaimed by Presidential Decree No. 940, Metro Manila as a whole is the Philippines' seat of government but the city of Manila is the capital. The largest city in the metropolis is Quezon City, while the largest business district is the Makati Central Business District.
In the Republic of Korea there are seven special and metropolitan cities at autonomous administrative levels. These are the most populous metropolitan areas in the country. In decreasing order of the population of 2015 census, they are Seoul, Busan, Incheon, Daegu, Daejeon, Gwangju and Ulsan.
According to the census of 2015, cities of Changwon and Suwon also qualify for being elevated to the level of metropolitan cities (having population over 1 million), but any future plans to promote them into metropolitan city are unlikely to be accepted because of political concerns about the structure of administrative divisions. There are also some county-level cities with increasing population near 1 million, namely Goyang, Yongin, and Seongnam, but they are also unlikely to be promoted into metropolitan city because they are all satellite cities of Seoul.
Taipei, the biggest city in Taiwan, is the political, economic, and cultural center of Taiwanese. The metropolitan area consists of 4 administrative districts (Taipei, New Taipei, Keelung, and Taoyuan) with more than 8 millions people inhabited.
Tashkent is Uzbekistan's most populous city and the only with over one million residents.
In Bosnia and Herzegovina, the country's capital Sarajevo is the only metropolis. Sarajevo is a political, economical, educational, cultural and infrastructural center. Moreover, Sarajevo has a region-wide influence in politics, education, entertainment, media, fashion, science, and the arts. With a metropolitan area of over 680 thousand, it is the third largest city in the region of former Yugoslavia. 
Only Prague has over a million residents.
In Denmark the only metropolis is Greater Copenhagen, consisting of the capital, Copenhagen, situated in the Capital Region of Denmark along with the neighboring regions Region Zealand and Skåne County (Sweden). Greater Copenhagen has an approximate population of 3.9 million people. This area is the most densely populated area in the Nordic Region.
France's national statistics institute, Insee, designates 12 of the country's urban areas as metropolitan areas. Paris, Lyon and Marseille are the biggest, the other nine being Toulouse, Lille, Bordeaux, Nice, Nantes, Strasbourg, Rennes, Grenoble and Montpellier.
The largest German city by administrative borders is Berlin, while Rhine-Ruhr is the largest metropolitan area (with more than 10 million people). The importance of a city is measured with three groups of indicators, also called metropolitan functions: The decision making and control function, the innovation and competition function, and the gateway function. These functions are seen as key domains for metropolitan regions in developing their performance.
In spatial planning, a metropolis is usually observed within its regional context, thus the focus is mainly set on the metropolitan regions. These regions can be mono central or multi central. Eleven metropolitan regions have been defined due to these indicators: Berlin-Brandenburg, Bremen-Oldenburg, Dresden-Halle-Leipzig, Frankfurt-Rhine-Main, Hamburg, Hannover-Braunschweig-Göttingen-Wolfsburg, Munich, Nuremberg, Rhine-Neckar, Rhine-Ruhr (with Cologne/Bonn), and Stuttgart.
As of January 1, 2015, there are 14 "metropolitan cities" in Italy. Rome, Milan, Naples and other big cores have taken in urban zones from their surrounding areas and merged them into the new entities, which have been home for one out of three Italians. The provinces remained in the parts of the country not belonging to any Città Metropolitana.
The Union of Polish Metropoles (Polish: Unia Metropolii Polskich), established in 1990, is an organization of the largest cities in the country. Currently twelve cities are members of the organization, of which 11 have more than a quarter-million inhabitants. The largest metropolitan area in Poland, if ranked solely by the number of inhabitants, is the Silesian Metropolis (in fact a metroplex), with around 3 million inhabitants (5 million inhabitants in the Silesian metropolitan area), followed by Warsaw, with around 1.8 million inhabitants in the city proper and 3.1 million in the Warsaw metropolitan area. The Silesian Metropolis is an initiative of recent years attempting to unite a large conurbation into one official urban unit. Other Polish metropoles are Kraków, ?ód?, Wroc?aw, Pozna?, Tricity, Szczecin and Bydgoszcz.
Spain has around 15 metropolitan areas with a population greater than 500,000 people. The largest metropoles with populations greater than a million people are Madrid, Barcelona, Valencia, and Sevilla.
Romania has one big metropolis, Bucharest with a population greater than 2,500,000 people. Other metropolitan areas with populations greater than a half million people are Cluj-Napoca, Iasi, Timisoara, Brasov, Constanta and Craiova.
In the UK, the term the Metropolis was used to refer to London, or the London conurbation. The term is retained by the London police force, the Metropolitan Police Service (the "Met"). The chief officer of the Metropolitan Police is formally known as the Commissioner of Police of the Metropolis. Since 1974 six conurbations (outside London) have been known as metropolitan counties, each divided into metropolitan districts. Other conurbations in the United Kingdom are also sometimes considered to be metropolitan areas, most notably the West Midlands (centred on the city of Birmingham), West Yorkshire (centred on the city of Leeds), Merseyside (centred on the city of Liverpool),Greater Manchester and Greater Glasgow which make up the most densely populated areas in the British Isles outside London.
The Government of Australia defines a metropolitan area as any statistical division or district with a population of more than 100,000. According to this definition, there are at least 16 metropolitan areas in Australia, including every state capital. By population the largest of these metropolitan areas is Sydney, New South Wales (urban area population at 2016 Census of 5,029,768) and the smallest is Darwin, Northern Territory (Urban area population at 2016 census of 145,916).
In France, Portugal, Spain, and the Netherlands, the word metropolis (métropole (Fr.) / metrópole (Port.) / metrópoli (Spa.) / metropool (Dutch)) designates the mainland part of a country situated on or close to the European mainland; in the case of France, this means France without its overseas departments. For Portugal and Spain during the Spanish Empire and Portuguese Empire period, the term was used to designate Portugal or Spain minus its colonies (the Ultramar). In France métropole can also be used to refer to a large urban agglomeration; for example, "La Métropole de Lyon" (the Lyon Metropolis).