More than half of humanity now lives in cities
A city is a substantial human settlement, yet no universal population floor exists—some places call tiny towns cities. After two centuries of rapid urbanization, over half the world is urban. Functional definitions stress roles as administrative, commercial, religious, and cultural hubs.
Census rules mix headcounts, density, dwellings, jobs, and infrastructure. U.S. state minima often sit between 1,500 and 5,000; globally, urban cutoffs range from 1,500 to 50,000. A European Commission–OECD–World Bank metric uses at least 50,000 people in contiguous cells above 1,500 per square kilometer. That UN-endorsed measure was adopted in March 2021 mainly so countries could be compared, while working definitions of a small city usually begin near 100,000 people.
Size alone does not suffice: literate elites, specialized trades, and symbolic status mark many historical cities. Australia leaves the definition to each state, and in the United Kingdom city status, once tied to having a diocesan cathedral, is now granted by the Crown, which is why St Davids counted only 1,751 residents in 2021.
The word travelled from Latin civitas, meaning citizenship or state, through Old French cité, and it sits close to the Greek polis that survives in metropolis; names of individual towns are called astionyms. Cities occupy only about 3 percent of the planet's land, and because water has always shaped where they grow, most urban people still live on a coast or a river. Since towns cannot feed themselves, they depend on a surrounding hinterland. Most have a core of economically, politically and religiously important buildings, which archaeologists call a temenos, or a citadel when walled.
Density brings trade-offs. Compact cities can shrink each resident's ecological footprint through efficient transport and smaller land use, which is why they feature in climate plans and in Sustainable Development Goal 11, yet they also create heat islands, concentrate pollution and strain water supplies.
Source: City
