a room or a group of related rooms, among similar sets in one building, designed for use as a dwelling.

a building containing or made up of such rooms.

any separated room or group of rooms in a house or other dwelling

We heard cries from an apartment at the back of the house.

apartments, British . a set of rooms used as a dwelling by one person or one family.

noun

accommodation , cave * , chambers , cold-water , condo , coop , cooperative , crash pad * , den * , digs , dump * , flat , living quarters , lodging , pad * , penthouse , rental , residence , suite , walk-up , abode , building , co-op , dwelling , pad , rooms , tenement , unit