Apartment

When part of a house is converted for the ostensible use of a landlord's family member, the unit may be known as an in-law apartment or granny flat, though these (sometimes illegally) created units are often occupied by ordinary renters rather than family members. In Canada these suites are commonly located in the basements of houses and are therefore normally called basement suites or "mother-in-law suites."
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.