World Urbanization Prospects

Term	Definition
Administrative reclassification	The process by which rural areas or towns are officially redesignated as urban areas by government authorities, often contributing to urban population growth without actual migration.
Annual growth rate	See: Average annual rate of change of the population.
Average annual rate of change of the population	Average exponential rate of growth of the population over a given period. It is calculated as ln(Pt/P0)/n where n is the length of the period and P is the rural population. It is expressed as a per cent.
Average rate of change of the percentage of the population	Average exponential rate of change of the percentage of the population over a given period. It is calculated as ln(percPt/percP0)/n where n is the length of the period and percP is the percentage of the population. It is expressed as a per cent.
Backcasting	A method for creating historical estimates by working backward from recent data using models and known totals, used here to reconstruct populations by settlement type before 1975.
Built-up area per person	The average amount of built-up land occupied per person, which is the ratio of built-up area to population.
Built-up surface/area	The gross building surface (including the thickness of the walls) bounded by the building wall perimeter. It measures any roofed structure erected above ground for any human use (including houses, factories, offices, religious and leisure buildings and structures in slums, informal settlements and refugees/IDP camps) that has been developed, not just where people live. The terms "built-up surface" and "built-up area" are used interchangeably in the text.
Capital cities	The designation of any specific city as a capital city is done solely on the basis of the designation as reported by the country or area. The city can be the seat of the government as determined by the country. Few countries designate more than one city to be a capital city with a specific title function (e.g., administrative and/or legislative capital).
Cities	According to the Degree of Urbanization methodology, contiguous geographic areas with a high population density (at least 1,500 people per km2) and a total population of at least 50,000 inhabitants.
Copernicus	Earth Observation (EO) component of the EU's Space programme. Copernicus is managed by the European Commission, and includes the Sentinel satellite missions (e.g. Sentinel-1 and Sentinel-2), developed by the European Space Agency (ESA), which collect images on the global environment.
Degree of Urbanization (DEGURBA)	A globally standardized method for classifying all areas of a country as cities, towns (or semi-dense areas), or rural areas. It uses a combination of population size, density, and contiguity thresholds based on 1 km² population grids and satellite data to provide a consistent measure of urbanization across countries. A finer subdivision of the three main groups is also available as: dense towns, semi-dense towns and suburban/peri-urban areas; and, for rural, villages, dispersed and very dispersed areas.
Functional Areas	Large city-centered zones used in projections to capture subnational differences (around 1,000 globally), improving how growth is distributed across space.
GHS-BUILT	GHSL's global grid of built-up area and volume derived from Landsat/Sentinel data with machine learning and expert validation.
GHS-POP	GHSL's gridded estimates of the resident population used to classify and analyze settlements under the Degree of Urbanization.
GHS-UCDB (Urban Centre Database)	A GHSL GIS dataset providing standardized information on urban centres worldwide.
Global Human Settlement Layer (GHSL)	A suite of global, open geospatial datasets that maps human settlements (buildings and their inhabitants) using satellite imagery and population data. It produces data on built-up areas and population distribution, which are key inputs for the Degree of Urbanization methodology.
Gridded population data	see Population Grid.
Gross National Income (GNI) per person	The total income generated by a country's residents and businesses, both at home and abroad, divided by the country's population. It is a common measure of a country's average income level and economic development.
In-situ urbanization	The process by which a rural area gradually develops urban features (such as improved infrastructure, services and non-agricultural jobs) while most residents remain in the same location.
Land area	The total geographic space within the boundaries of a settlement, city or region, including both developed land (built-up areas) and open spaces, such as parks, fields, water bodies and undeveloped land. It is often used to calculate population density and, in this report, refers to the sum of 1 km² grid cells assigned to each Degree of Urbanization category, whether or not those cells are built-up.
Land consumption	The conversion of natural or agricultural land for urban development, measured as the amount of land used per person.
Landlocked developing countries (LLDCs)	Developing countries with no direct access to the sea, facing geographic isolation that creates significant economic challenges, including high transportation costs and difficulties participating in global trade.
Landsat	The Landsat programme consists of a series of EO satellite missions, jointly managed by the US National Aeronautics and Space Administration (NASA), and the US Geological Survey (USGS). Since 1972, Landsat satellites have continuously acquired images of the Earth's land surface and provided an uninterrupted data archive on natural resources and the environment.
Least developed countries (LDCs)	A group of the world's poorest countries, as defined by the United Nations, which face severe structural impediments to sustainable development. They are characterized by low income, limited human resources and high economic vulnerability.
Megacity	A very large city, typically defined as having a population of 10 million or more inhabitants.
National definitions of "urban"	The set of criteria national authorities use to classify an area as urban for their own statistical or administrative purposes. These criteria can include factors such as administrative status, population size/density and economic and/or functional characteristics.
National urban policy	A government framework that coordinates urban development strategies, infrastructure planning, and service delivery across the country.
New Urban Agenda	A global framework adopted by the United Nations in 2016 that sets out a shared vision for sustainable urban development and provides guidelines for planning, designing and managing cities to create more inclusive, safe, resilient and sustainable urban areas.
Percentage rural	Rural population based on national definition, or population living in rural areas (based on DEGURBA) as a percentage of the total population.
Percentage urban	Urban population based on national definition, or population living in cities and towns (based on DEGURBA) as a percentage of the total population.
Peri-urban/suburban	Zones on the outskirts of cities that mix urban and rural features. They often have intermediate population densities, are functionally connected to the city and experience rapid change and development. They are included within "towns and semi-dense areas" in terms of Degree of Urbanization.
Population density	The number of people living in a given area, usually expressed as people per km2. It shows how concentrated or spread out a population is, with a high density being a common feature of cities.
Population grid	A method of mapping population distribution using a regular grid system made of small, uniform cells of 1 km² and estimating the number of people living in each cell. This provides a more detailed view of where people live than traditional administrative boundaries and supports analyses such as the Degree of Urbanization.
Remote sensing	The use of satellite technology to collect information about the Earth's surface without direct physical contact.
Rural areas	Areas with low population density, typically below 300 people per km2, or small settlements that are not part of a city or town. These include villages and dispersed communities under the Degree of Urbanization classification.
Rural population	De facto population living in areas classified as rural based on national or DEGURBA definitions. Data refer to 1 July of the year indicated and are presented in thousands.
Satellite imagery	Photographs or digital images of the Earth taken from satellites that are used to monitor land use, urban growth and environmental changes.
SDG regions	Geographic groupings of countries used by the United Nations to track progress toward the Sustainable Development Goals.
Settlement continuum	The concept that human settlements exist along a spectrum from rural to urban, rather than in distinct categories.
Settlement hierarchy	The organization of settlements by size and function, from small villages to large cities, showing their relationships and roles.
Small island developing States (SIDS)	A group of developing countries comprising small islands and low-lying coastal states. They face unique challenges owing to their small size, remoteness and high vulnerability to climate change, natural hazards and economic shocks.
Sustainable Development Goals (SDGs)	A set of 17 global goals adopted by the United Nations in 2015 as a blueprint for achieving a better and more sustainable future by 2030. They address challenges such as poverty, inequality and climate change. Goal 11 focuses on making cities and human settlements inclusive, safe, resilient and sustainable.
Total population	De facto population in a country, area or region as of 1 July of the year indicated. Figures are presented in thousands.
Towns and semi-dense areas	Urban clusters outside cities with moderate population density (at least 300 people per km2) and a minimum of about 5,000 inhabitants. These areas often include suburban and peri-urban zones and fall between cities and rural areas under the Degree of Urbanization classification. In the text, "towns" is used as a shorthand for "towns and semi-dense areas".
Urban agglomeration	A continuous urban area formed by a city and its surrounding developed areas, regardless of administrative boundaries.
Urban compactness	A measure of how efficiently urban areas use land, with compact cities having a higher density and less sprawl.
Urban Population	De facto population living in areas classified as urban according to the criteria used by each area or country, or population living in cities and towns (based on DEGURBA). Data refer to 1 July of the year indicated and are presented in thousands.
Urban sprawl	The uncontrolled expansion of urban areas into surrounding regions, typically characterized by low-density development and increased land consumption.
Urbanization	The process by which an increasing share of people lives in urban areas. This occurs through both migration from rural areas to cities and the gradual transformation of rural areas into urban ones.
Urban-rural continuum	The concept that human settlements exist along a gradual transition from urban to rural characteristics rather than in separate categories. At one end are dense cities, and at the other are sparsely populated rural areas, with towns and semi-dense areas in between, all connected as part of a single system.

Department of Economic and Social Affairs

Population Division

World Urbanization Prospects 2025