Apartment

A maisonette is an apartment with more than one floor.
In Milwaukee vernacular architecture, a Polish flat is an existing small house or cottage that has been lifted up to accommodate the creation of a new basement floor housing a separate apartment, then set down again; thus becoming a modest two-story flat.
In Russia, a communal apartment («коммуналка») is a room with a shared kitchen and bath. A typical arrangement is a cluster of five or so apartments with their common kitchen and bathroom and their own front door, occupying a floor in a pre-Revolutionary mansion. Traditionally a room is owned by the government and assigned to a family on a semi-permanent basis.