noun

• (chiefly Canada, US, Australia, Philippines) A complete domicile occupying only part of a building, especially one for rent; a flat.
• (archaic) A suite of rooms within a domicile, designated for a specific person or persons and including a bedroom.
• (obsolete) A division of an enclosure that is separate from others; a compartment
• (computing, COM) 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.