an apartment (american english), or flat (british english, indian english) is a self-contained housing unit (a type of residential real estate) that occupies only part of a building, generally on a single storey. there are many names for these overall buildings, see below. the housing tenure of apartments also varies considerably, from large-scale public housing, to owner occupancy within what is legally a condominium (strata title or commonhold), to tenants renting from a private landlord (see leasehold estate).