An apartment (in American English) or flat in British English is a self-contained housing unit (a type of residential real estate) that occupies only part of a building. Such a building may be called an apartment building, apartment house (in American English), block of flats, tower block, high-rise or, occasionally mansion block (in British English), especially if it consists of many apartments for rent. Apartments may be owned by an owner/occupier by leasehold tenure or rented by tenants (two types of housing tenure).
The term apartment is favored in North America (although flat is used in the case of a unit which is part of a house containing two or three units, typically one to a floor), whereas the term flat is commonly, but not exclusively, used in the United Kingdom, Ireland, Singapore, Hong Kong and most Commonwealth nations.
In Malaysian English, flat often denotes a housing block of lesser quality meant for lower-income groups, while apartment is more generic and may also include luxury condominiums. This usage has also been appearing in British English where apartment is used to denote expensive 'flats' in exclusive and expensive residential areas in, for example, parts of London such as Belgravia and Hampstead.