A city is a human settlement of a substantial size. The term "city" has different meanings around the world and in some places the settlement can be very small. Even where the term is limited to larger settlements, there is no universally agreed definition of the lower numerical boundary for their size. In a more specific sense, a city can be defined as a permanent and densely populated place with administratively defined boundaries whose members work primarily on non-agricultural tasks. Cities generally have extensive systems for housing, transportation, sanitation, utilities, land use, production of goods, and communication. Their density facilitates interaction between people, government organizations, and businesses, sometimes benefiting different parties in the process, such as improving the efficiency of goods and service distribution.
Historically, city dwellers had been a small proportion of humanity overall, but following two centuries of unprecedented and rapid urbanization, more than half of the world population now lives in cities, which has had profound consequences for global sustainability. Present-day cities usually form the core of larger metropolitan areas and urban areas—creating numerous commuters traveling toward city centres for employment, entertainment, and education. However, in a world of intensifying globalization, all cities are to varying degrees also connected globally beyond these regions. This increased influence means that cities also have significant influences on global issues, such as sustainable development, climate change, and global health. Because of these major influences on global issues, the international community has prioritized investment in sustainable cities through Sustainable Development Goal 11. Due to the efficiency of transportation and the smaller land consumption, dense cities hold the potential to have a smaller ecological footprint per inhabitant than more sparsely populated areas. Therefore, compact cities are often referred to as a crucial element in fighting climate change. However, this concentration can also have some significant harmful effects, such as forming urban heat islands, concentrating pollution, and stressing water supplies and other resources.
Meaning Urban settlements Common population definitions for an urban area (city or town) range between minimum values of 1,500 and 50,000 people, with most U.S. states using a minimum between 1,500 and 5,000 inhabitants."Table 6 " in United Nations Demographic Yearbook (2015 ), the 1988 version of which is quoted in Carter (1995), pp. 10–12. Some jurisdictions set no such criteria.
National censuses use a variety of definitions – invoking factors such as population, population density, number of dwellings, economic function, and infrastructure – to classify populations as urban.
City
A city can be distinguished from other human settlements by its relatively great size, but also by its functions and its special symbolic status. The term can refer either to the physical streets and buildings of the city or to the collection of people who dwell there and can be used in a general sense to mean urban rather than rural territory.Lynch, Kevin A., "What Is the Form of a City, and How Is It Made?"; in Marzluff et al. (2008), p. 678. "The city may be looked on as a story, a pattern of relations between human groups, a production and distribution space, a field of physical force, a set of linked decisions, or an arena of conflict. Values are embedded in these metaphors: historic continuity, stable equilibrium, productive efficiency, capable decision and management, maximum interaction, or the progress of political struggle. Certain actors become the decisive elements of transformation in each view: political leaders, families and ethnic groups, major investors, the technicians of transport, the decision elite, the revolutionary classes."
According to the "functional definition", a city is not distinguished by size alone, but also by the role it plays within a larger political context. Cities serve as administrative, commercial, religious, and cultural hubs for their larger surrounding areas.Marshall (1989), pp. 14–15. The presence of a literate elite is often associated with cities because of the cultural diversities present in a city.Prokopovych, M. (13 May 2015). Literary and artistic metropolises. EGO. Retrieved 5 March 2023, from http://ieg-ego.eu/en/threads/crossroads/courts-and-cities/markian-prokopovych-rosemary-h-sweet-literary-and-artistic-metropolisesKaplan et al. (2004), pp. 23–24. A typical city has professional administrators, regulations, and some form of taxation (food and other necessities or means to trade for them) to support the government workers. (This arrangement contrasts with the more typically horizontal relationships in a tribe or village accomplishing common goals through informal agreements between neighbors, or the leadership of a chief.) The governments may be based on heredity, religion, military power, work systems such as canal-building, food distribution, land-ownership, agriculture, commerce, manufacturing, finance, or a combination of these. Societies that live in cities are often called civilizations.
Population size, density The degree of urbanization is a modern metric to help define what comprises a city: "a population of at least 50,000 inhabitants in contiguous dense grid cells (>1,500 inhabitants per square kilometer)". This metric was "devised over years by the European Commission, OECD, World Bank and others, and endorsed in March by the United Nations ... largely for the purpose of international statistical comparison". Typical working definitions for small-city populations start at around 100,000 people.
In specific countries In Australia, the definition of what constitutes a city varies between the states.
In the United Kingdom, city status was once confined to settlements with diocesan cathedrals. It is now awarded by the Crown and then remains permanent, with only two exceptions to this rule, due to policy changes. The traditional cathedral criterion results in some very small cities, notably St Davids with a population of 1,751 .
Etymology
The word city comes from the , itself from the , meaning "citizenship" or "state". The related (maybe) civilization come from the Latin root , originally meaning 'citizenship' or 'community member' and eventually coming to correspond with , meaning 'city' in a more physical sense."city, n.", Oxford English Dictionary, June 2014. The Roman civitas was closely linked with the Greek —another common root appearing in English words such as metropolis.
In toponymic terminology, names of individual cities and towns are called astionyms (from Ancient Greek 'city or town' and 'name').
Geography Urban geography deals both with cities in their larger context and with their internal structure.Carter (1995), pp. 5–7. "[...] the two main themes of study introduced at the outset: the town as a distributed feature and the town as a feature with internal structure, or in other words, the town in area and the town as area." Cities are estimated to cover about 3% of the land surface of the Earth.
Site
Town siting has varied through history according to natural, technological, economic, and military contexts. Access to water has long been a major factor in city placement and growth, and despite exceptions enabled by the advent of rail transport in the nineteenth century, through the present most of the world's urban population lives near the coast or on a river.Marshall (1989), pp. 11–14.
Urban areas as a rule cannot produce their own food and therefore must develop some relationship with a hinterland that sustains them.Kaplan et al. (2004), pp. 155–156. Only in special cases such as mining towns which play a vital role in long-distance trade, are cities disconnected from the countryside which feeds them.Marshall (1989), p. 15. "The mutual interdependence of town and country has one consequence so obvious that it is easily overlooked: at the global scale, cities are generally confined to areas capable of supporting a permanent agricultural population. Moreover, within any area possessing a broadly uniform level of agricultural productivity, there is a rough but definite association between the density of the rural population and the average spacing of cities above any chosen minimum size." Thus, centrality within a productive region influences siting, as economic forces would, in theory, favor the creation of marketplaces in optimal mutually reachable locations.
Center
The vast majority of cities have a central area containing buildings with special economic, political, and religious significance. Archaeologists refer to this area by the Greek term temenos or if fortified as a citadel.Kaplan et al. (2004), pp. 34–35. "In the center of the city, an elite compound or temenos was situated. Study of the very earliest cities show this compound to be largely composed of a temple and supporting structures. The temple rose some 40 feet above the ground and would have presented a formidable profile to those far away. The temple contained the priestly class, scribes, and record keepers, as well as granaries, schools, crafts—almost all non-agricultural aspects of society." These spaces historically reflect and amplify the city's centrality and importance to its wider sphere of influence.: "From the simplest forms of exchange, when peasant farmers literally brought their produce from the fields into the densest point of interaction—giving us market towns—the significance of central places to surrounding territories began to be asserted. As cities grew in complexity, the major civic institutions, from seats of government to religious buildings, would also come to dominate these points of convergence. Large central squares or open spaces reflected the importance of collective gatherings in city life, such as Tiananmen Square in Beijing, the Zócalo in Mexico City, the Piazza Navonae in Rome and Trafalgar Square in London." Today cities have a city center or downtown, sometimes coincident with a central business district.
Public space
Cities typically have public spaces where anyone can go. These include privately owned spaces open to the public as well as forms of public land such as public domain and the commons. Western philosophy since the time of the Greek agora has considered physical public space as the substrate of the symbolic public sphere. Public art adorns (or disfigures) public spaces. Parks and other natural sites within cities provide residents with relief from the hardness and regularity of typical built environments. Urban green spaces are another component of public space that provides the benefit of mitigating the urban heat island effect, especially in cities that are in warmer climates. These spaces prevent carbon imbalances, extreme habitat losses, electricity and water consumption, and human health risks.
Internal structure
The urban structure generally follows one or more basic patterns: geomorphic, radial, concentric, rectilinear, and curvilinear. The physical environment generally constrains the form in which a city is built. If located on a mountainside, urban structures may rely on terraces and winding roads. It may be adapted to its means of subsistence (e.g. agriculture or fishing). And it may be set up for optimal defense given the surrounding landscape.Moholy-Nagy (1968), 21–33. Beyond these "geomorphic" features, cities can develop internal patterns, due to natural growth or to city planning.