An apartment or a flat is a self-contained housing unit (a type of residential real estate) that occupies only part of a building, correctly, on a single level without a stair. Such a building may be called an apartment building, apartment complex, flat complex, block of flats, tower block, high-rise or, occasionally mansion block , especially if it consists of many apartments for rent. In Scotland it is called a block of flats or, if it's a traditional sandstone building, 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).