An arch is a curved masonry structure that spans a space and supports structure and weight above it. Masonry semi-circular arches made of precast stone are generally seen at entrances, doors and windows.
A vault is a roof in the form of an arch or a series of arches. It is an arched structure, usually of masonry or concrete, serving to cover a space. A vault provides a building or a room with an arched roof. Vaulting is similar to an arch, dome, crypt, or cellar.
A masonry ceiling is an overhead interior surface the covers the upper limit of a room. It can be brick or stone and it need not be a structural element.