the upper or overhead surface of a room
top of a room
Cases of word usage
1) a support for several lights hanging from a ceiling (chandelier)
2) (the movable covering over) an opening in a ceiling or floor, especially (hatchway) one in a ship's deck through which cargo is lowered and raised (hatch)
3) one of the pieces of wood (from wall to wall) to which floors are fastened; a steel bar supporting a floor or ceiling (joist)