A neighbourhood or neighborhood (see spelling differences) is a geographically localised community within a larger city, town or suburb. Neighbourhoods are often social communities with considerable face-to-face interaction among members.
In the words of the urban scholar Lewis Mumford, “Neighbourhoods, in some primitive, inchoate fashion exist wherever human beings congregate, in permanent family dwellings; and many of the functions of the city tend to be distributed naturally—that is, without any theoretical preoccupation or political direction—into neighbourhoods.”  Most of the earliest cities around the world as excavated by archaeologists have evidence for the presence of social neighbourhoods. Historical documents shed light on neighbourhood life in numerous historical preindustrial or nonwestern cities.
Neighbourhoods are typically generated by social interaction among people living near one another. In this sense they are local social units larger than households not directly under the control of city or state officials. In some preindustrial urban traditions, basic municipal functions such as protection, social regulation of births and marriages, cleaning and upkeep are handled informally by neighbourhoods and not by urban governments; this pattern is well documented for historical Islamic cities.
In addition to social neighbourhoods, most ancient and historical cities also had administrative districts used by officials for taxation, record-keeping, and social control. Administrative districts are typically larger than neighbourhoods and their boundaries may cut across neighbourhood divisions. In some cases, however, administrative districts coincided with neighbourhoods, leading to a high level of regulation of social life by officials. For example, in the T’ang period Chinese capital city Chang’an, neighbourhoods were districts and there were state officials who carefully controlled life and activity at the neighbourhood level.
Neighbourhoods in preindustrial cities often had some degree of social specialization or differentiation. Ethnic neighbourhoods were important in many past cities and remain common in cities today. Economic specialists, including craft producers, merchants, and others, could be concentrated in neighbourhoods, and in societies with religious pluralism neighbourhoods were often specialized by religion. One factor contributing to neighbourhood distinctiveness and social cohesion in past cities was the role of rural to urban migration. This was a continual process in preindustrial cities, and migrants tended to move in with relatives and acquaintances from their rural past.
Neighbourhoods have several advantages as areas for policy analysis as well as an arena for social action:
But in addition to these benefits, considerable research indicates that strong and cohesive neighbourhoods and communities are linked –quite possibly causally linked – to decreases in crime, better outcomes for children, and improved physical and mental health. The social support that a strong neighbourhood may provide can serve as a buffer against various forms of adversity.
There is some evidence that neighbourhoods tend to form personalities based upon certain sociological characteristics of the female inhabitants.
In the mainland of the People's Republic of China, the term is generally used for the urban administrative division found immediately below the district level, although an intermediate, subdistrict level exists in some cities. They are also called streets (administrative terminology may vary from city to city). Neighbourhoods encompass 2,000 to 10,000 families. Within neighbourhoods, families are grouped into smaller residential units or quarters of 100 to 600 families and supervised by a residents' committee; these are subdivided into residents' small groups of fifteen to forty families. In most urban areas of China, neighbourhood, community, residential community, residential unit, residential quarter have the same meaning: 社区 or 小区 or 居民区 or 居住区, and is the direct sublevel of a subdistrict (街道办事处), which is the direct sublevel of a district (区), which is the direct sublevel of a city (市). (See Political divisions of China)
In Canada and the United States, neighbourhoods are often given official or semi-official status through neighbourhood associations, neighbourhood watches, or block watches. These may regulate such matters as lawn care and fence height, and they may provide such services as block parties, neighbourhood parks, and community security. In some other places the equivalent organization is the parish, though a parish may have several neighbourhoods within it depending on the area.
In localities where neighbourhoods do not have an official status, questions can arise as to where one neighbourhood begins and another ends. Many cities use districts and wards as official divisions of the city, rather than traditional neighbourhood boundaries.
The term has no general official or statistical purpose in the United Kingdom, but is often used by local boroughs for self-chosen sub-divisions of their area for the delivery of various services and functions, or is used as an informal term to refer to a small area within a town or city. The label is commonly used to refer to organisations which relate to such a very local structure, such as neighbourhood policing or Neighbourhood watch schemes.