The glossary

Planning terms are often rooted in the administrative and planning culture of a particular country and cannot be straightforwardly translated.

The English-language glossary presented here is intended to offer a translation and elucidation of central terms in the German planning system to a non-German speaking readership in the interests of facilitating discourse.

Our intention is to ensure as much consistency as possible in the key terms used throughout this platform and the publications of the ARL that can be found here.

The definitions used are based on those found in the national glossary for Germany, which was elaborated in the framework of the BSR INTERREG III B project COMMIN.

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Agglomeration, agglomeration areaAgglomeration, Agglomerationsraum

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An (urban) agglomeration (largely synonymous with conurbation, metropolitan area) is a concentration of settlements consisting of interlinked and interdependent communities distinguished from surrounding areas by greater settlement density and a higher proportion of built development. As a rule, agglomerations form around one or more core cities surrounded by heavily built-up inner rings of suburbs and geographically more extensive, partly rural catchment areas.

The core or central city with the suburban belt is referred to as an urban region. Major cities with international status and their extensive catchment areas are termed metropolitan regions. With a high concentration of housing and workplaces, urban agglomerations drive economic development and are loci of cultural life. They are accordingly important for the country as a whole. In terms of spatial category, agglomerations or conurbations are the type of area with the highest use density, being the opposite pole to sparsely population rural areas. Communication axes between agglomerations, which partly traverse rural areas, are termed corridors.


Important elements in spatial planning, axes are constituted by a concentration of transport and supply routes (linear infrastructure) and a relatively close succession of development centres and central places. Depending on physical features and functions, a distinction is made between communications axes (supralocal axes) and settlement axes. Communications axes connect differently ranking central places and offer locational advantages at transport interchanges or nodes.

Supralocal axes are national or European communication axes. Settlement axes are axes in agglomerations formed by a close succession of settlements along the routes of existing or planned public-transport services. They do not necessarily form an unbroken ribbon of development but can be separated by open spaces. Spatial planning attempts to concentrate development along settlement axes to exploit existing public transport services more effectively and to preserve open spaces between axes.