Agglomerations / metropolitan areas (A) include a central city and neighboring towns (suburbs) forming a connected region of dense, predominately urban population. Their population is economically and culturally linked to the central city (e.g. by commuters). Some agglomerations have more than one central city (e.g. "The Ruhr"). Mostly, the components of an agglomeration are small administrative divisions like communes. Neighboring agglomerations may form one agglomeration complex (AC).
Area (A) is the total surface of a country, of its administrative divisions or of cities. It includes land and (non-tidal) inland water area. Land area (A-L) excludes inland water area.
Each country has its own definition what the term city (C) means. Here, it refers to the smallest administrative unit of a country having a predominately urban population. Small cities are often called towns, villages or settlements.
A municipio (M) is the smallest administrative unit of many countries in Latin America. It typically covers a relatively large area and has a high portion of rural population. Therefore, the urban population of a municipio (C, MU) is mostly given as its city population.
population (census/estimate/projection)
Census population (C) is determined by a census typically performed every 5 or 10 years. The first results of census are often provisional (Cp); they may be higher or lesser than the final results (Cf). Census results mostly show some underenumeration that may be adjusted by estimates (Ca). Estimates (E) are based on calculations using the current birth and death rates and the estimated migration or they are based on population registers. Estimates refer to a given time in the past. Projections (P) are calculations referring to the future; their accuracy is often poor.
population (de jure/de facto)
The de facto population (f) is the population actually present at a given time including temporary residents and excluding residents temporarily absent. The de jure population (j) is the legally resident population including residents temporarily absent and excluding temporary residents.
urban area
Urban areas (UA) are densely populated urban regions typically linked by continuous built-up areas. They may cover parts of one or of more cities/communes; their borders do not coincide with the boundaries of adminitrative units. Therefore, urban areas have more or less inhabitants than the central city. Urban population is largely non-agriculturally oriented. Each country has its own definition of urban and rural.