Etymology and usage
The English word is derived from the Old French subburbe, which is in turn derived from the Latin suburbium, formed from sub (meaning "under" or "below") and urbs ("city"). The first recorded usage of the term in English, was made by John Wycliffe in 1380, where the form subarbis was used, according to the Oxford English Dictionary.
Australia and New Zealand
In Australia and New Zealand, suburbs (in the wider sense noted in the lead paragraph) have become formalised as geographic subdivisions of a city and are used by postal services in addressing. In rural areas in both countries, their equivalents are called localities (see suburbs and localities). The terms inner suburb and outer suburb are used to differentiate between the higher-density areas in proximity to the city centre (which would not be referred to as 'suburbs' in most other countries), and the lower-density suburbs on the outskirts of the urban area. The term 'middle suburbs' is also used. Inner suburbs, such as Te Aro in Wellington, Eden Terrace in Auckland, Prahran in Melbourne and Ultimo in Sydney, are usually characterised by higher density apartment housing and greater integration between commercial and residential areas.
In New Zealand, most suburbs are not legally defined which can lead to confusion as to where they may begin and end. Although there is a geospatial file defining suburbs for use by emergency services developed and maintained by Fire and Emergency New Zealand (formerly the New Zealand Fire Service), in collaboration with other government agencies, to date this file has not been released publicly. New Zealand company Koordinates Limited requested access to the geospatial file under the Official Information Act 1982 but this request was rejected by the New Zealand Fire Service on the basis that it would prejudice the health & safety of, or cause material loss, to the public. In September 2014 a decision was made by the Ombudsman of New Zealand ruling that the New Zealand Fire Service refusal to release the geospatial file without agreeing to terms which included, among other restrictions, a prohibition on redistribution of the geospatial file, was reasonable.
Britain and Ireland
In the United Kingdom and in Ireland, suburb merely refers to a residential area outside the city centre, regardless of administrative boundaries. Suburbs, in this sense, can range from areas that seem more like residential areas of a city proper to areas separated by open countryside from the city centre. In large cities such as London and Leeds, suburbs include formerly separate towns and villages that have been gradually absorbed during a city's growth and expansion, such as Ealing, Bromley, and Guiseley.
In the United States and Canada, suburb can refer either to an outlying residential area of a city or town or to a separate municipality or unincorporated area outside a town or city.