An apartment builing, block of flats or tenement, is a multi-unit dwelling made up of several (generally four or more) apartments (US), or flats (UK; Chicago, Illinois). A difference may be drawn such as in San Francisco, California between an apartment and a flat, where an apartment is one of many units on a floor and a flat is the only unit on a given floor. Where the building is a high-rise construction, it is termed a tower block in the UK and elsewhere. The term apartment building is used regardless of height in the US.