Gentrification: the class and racial transformation of the central city. The central city: goods and services available to many people. Overurbanization: occurs when cities grow more rapidly than they can sustain jobs and housing. In these circumstances slums are produced-shacks set on unpaved streets, often with open sewers and no basic utilities. In general it is the rate, not the level, of urbanization that produces slums; higher evels of urbanizations are related to relatively fewer slums: most extensive slums- cities of sub-saharan africa. Public-private partnership: because of the signifigant costs and risks involved, urban regeneration strategies are usually undertaken in this form between city governments and real estate developers. Regeneration: involves the physical redevelopment of land where the existing buildings are no longer useful or profitable. It often takes place on brownfield sites- former industrial or commercial land where future use is affected by real or perceived environmental contamination. Urbanization: increasing concentration of population growing metropolitan areas.