In the study of human settlements, an urban agglomeration is an extended city
A city is a relatively large and permanent settlement. Although there is no agreement on how a city is distinguished from a town within general English language meanings, many cities have a particular administrative, legal, or historical status based on local law.For example, in the U.S...

 or town
A town is a human settlement larger than a village but smaller than a city. The size a settlement must be in order to be called a "town" varies considerably in different parts of the world, so that, for example, many American "small towns" seem to British people to be no more than villages, while...

 area comprising the built-up area of a central place (usually a municipality
A municipality is essentially an urban administrative division having corporate status and usually powers of self-government. It can also be used to mean the governing body of a municipality. A municipality is a general-purpose administrative subdivision, as opposed to a special-purpose district...

) and any suburb
The word suburb mostly refers to a residential area, either existing as part of a city or as a separate residential community within commuting distance of a city . Some suburbs have a degree of administrative autonomy, and most have lower population density than inner city neighborhoods...

s linked by continuous urban area
Urban area
An urban area is characterized by higher population density and vast human features in comparison to areas surrounding it. Urban areas may be cities, towns or conurbations, but the term is not commonly extended to rural settlements such as villages and hamlets.Urban areas are created and further...

. In France, INSEE
INSEE is the French National Institute for Statistics and Economic Studies. It collects and publishes information on the French economy and society, carrying out the periodic national census. Located in Paris, it is the French branch of Eurostat, European Statistical System...

 the French Statistical Institute, translate it as "Unité urbaine
Unité urbaine
In France an unité urbaine is a statistical area defined by INSEE, the French national statistics office, for the measurement of contiguously built-up areas...

" which means continuous urbanized area. However, because of differences in definitions of what does and does not constitute an "agglomeration", as well as variations and limitations in statistical or geographical methodology, it can be problematic to compare different agglomerations around the world. It may not be clear, for instance, whether an area should be considered to be a satellite and part of an agglomeration, or a distinct entity in itself.

The term "agglomeration" can also be linked to "Conurbation
A conurbation is a region comprising a number of cities, large towns, and other urban areas that, through population growth and physical expansion, have merged to form one continuous urban and industrially developed area...

", which is a more specific term for large urban clusters where the built-up zones of influence of distinct cities or towns are connected by continuous built-up development (Essen
- Origin of the name :In German-speaking countries, the name of the city Essen often causes confusion as to its origins, because it is commonly known as the German infinitive of the verb for the act of eating, and/or the German noun for food. Although scholars still dispute the interpretation of...

 - Dortmund
Dortmund is a city in Germany. It is located in the Bundesland of North Rhine-Westphalia, in the Ruhr area. Its population of 585,045 makes it the 7th largest city in Germany and the 34th largest in the European Union....

 and others in the Rhine-Ruhr district), even in different regions, states or countries, Lille
Lille is a city in northern France . It is the principal city of the Lille Métropole, the fourth-largest metropolitan area in the coun