A city is a human settlement of a notable 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 boundary for their size.[1][2] In a more narrow sense, a city can be defined as a permanent and densely settled place with administratively defined boundaries whose members work primarily on non-agricultural tasks.[3] Cities generally have extensive systems for housing, transportation, sanitation, utilities, land use, production of goods, and communication.[4][5] 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 have 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.[6][7][8][9][10] 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.[11][12] Therefore, compact cities are often referred to as a crucial element in fighting climate change.[13][14][15] However, this concentration can also have significant negative consequences, such as forming urban heat islands, concentrating pollution, and stressing water supplies and other resources.
Other important traits of cities besides population include the capital status and relative continued occupation of the city. For example, country capitals such as Beijing, Jakarta, Kuala Lumpur, London, Manila, Mexico City, Moscow, Nairobi, New Delhi, Paris, Rome, Seoul, Singapore, Tokyo, and Washington, D.C. reflect the identity and apex of their respective nations.[16] Some historic capitals, such as Istanbul, Yogyakarta, and Xi'an, maintain their reflection of cultural identity even without modern capital status. Religious holy sites offer another example of capital status within a religion; examples include Jerusalem, Mecca, Varanasi, Ayodhya, Haridwar, and Prayagraj.
A city can be distinguished from other human settlements by its relatively great size, but also by its functions and its special symbolic status, which may be conferred by a central authority. The term can also 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.[18][19]