An apartment (in American English) or a 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. In Scotland it is often called a tenement, which has a pejorative connotation elsewhere. 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) and also is the preferred term in Ireland. The term flat is commonly, but not exclusively, used in the United Kingdom, 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.In Australian English, the term flat was traditionally used, but the term apartment is also frequently used, as is "unit," short for "home unit".Tenement law refers to the feudal basis of permanent property such as land or rents. It may be found combined as in "Messuage or Tenement" to encompass all the land, buildings and other assets of a property.In the United States, some apartment-dwellers own their own apartments, either as co-ops, in which the residents own shares of a corporation that owns the building or development; or in condominiums, whose residents own their apartments and share ownership of the public spaces. Most apartments are in buildings designed for the purpose, but large older houses are sometimes divided into apartments. The word apartment denotes a residential unit or section in a building. In some locations, particularly the United States, the word connotes a rental unit owned by the building owner, and is not typically used for a condominium.In the UK, some flat owners own shares in the company that owns the freehold of the building as well as holding the flat under a lease. This is commonly known as a "share of freehold" flat. The freehold company has the right to collect annual ground rents from each of the flat owners in the building. The freeholder can also develop or sell the building, subject to the usual planning and restrictions that might apply.In some countries the word unit is a more general term referring to both apartments and rental business suites. The word is generally used only in the context of a specific building; e.g., "This building has three units" or "I'm going to rent a unit in this building", but not "I'm going to rent a unit somewhere." In Australia, a unit refers to flats, apartments or even semi-detached houses. Some buildings can be characterized as mixed use buildings, meaning part of the building is for commercial, business, or office use, usually on the first floor or first couple of floors, and there are one or more apartments in the rest of the building, usually on the upper floors.