An apartment is a self-contained housing unit that occupies only part of a building. Such a building may be called an apartment building, apartment complex , apartment house, 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 its 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. In some parts of the world, the word apartment refers to a new purpose-built self-contained residential unit in a building, whereas the word flat means a converted self-contained unit in an older building. An industrial, warehouse, or commercial space converted to an apartment is commonly called a loft, although some modern lofts are built by design. An apartment consisting of the top floor of a high apartment building can be called a penthouse.