Within a urban area there is a tenency for land uses to aggregate. A residential area is a land use in which the predominant use is housing. Housing may vary significantly between, and through, residential areas. These include single family housing, multiple family housing such as (apartments, duplexes, townhomes (or similar configurations), condominiums) or mobile homes. Zoning for residential use may permit some services or work opportunities or may totally exclude business and industry. It may permit high density land use or only permit low density uses. Residential zoning usually includes a smaller FAR (floor to area ratio) than business, commercial or industrial/manufacturing zoning.