A ceiling (pronounced /ˈsiːlɪŋ/) is an overhead interior surface that covers the upper limit of a room. It is generally not a structural element, but a finished surface concealing the underside of the floor or roof structure above.
Ceilings are classified according to their appearance or construction. A cathedral ceiling is any tall ceiling area similar to those in a church. A dropped ceiling is one in which the finished surface is constructed anywhere from a few inches to several feet below the structure above it. This may be done for aesthetic purposes, such as achieving a desirable ceiling height; or practical purposes such as providing a space for HVAC or piping. An inverse of this would be a raised floor. A concave or barrel shaped ceiling is curved or rounded, usually for visual or acoustical value, while a coffered ceiling is divided into a grid of recessed square or octagonal panels, also called a lacunar ceiling. A cove ceiling uses a curved plaster transition between wall and ceiling; it is named for cove molding, a molding with a concave curve.[1]