What is the meaning of Apartment?

A complete domicile occupying only part of a building, especially one for rent; a flat.

A suite of rooms within a domicile, designated for a specific person or persons and including a bedroom.

A division of an enclosure that is separate from others; a compartment

A conceptual space used for separation in the threading architecture. Objects in one apartment cannot directly access those in another, but must use a proxy.

Source: wiktionary.org