In classical architecture the cornice is the set of projecting moldings that crown an entablature. The cornice lies above the frieze, which rests on the architrave. The function of the projecting cornice is to throw rainwater free of the building's walls. In non-classical building practice, this function is handled by eaves and gutters, and in modernist architecture the elimination of the cornice has been important enough, often simply for demands of style, that elaborate internal drainage systems are provided.

A pediment is formed under the gable end of a building, where the cornice is carried across the wall at the height of the eaves and repeated above, under the roof line.

The cornice, by extension. becomes any horizontal molded projection which crowns an element: the cornice of a door or window, for instance, or the cornice of a pedestal. A simple cornice may be formed just with a crown molding.

Each of the Classic orders has certain characteristic profiles to its cornice:

The cornice of the Doric order

The cornice of the Ionic order

The cornice of the Corinthian order

In Italianate Architecture, a Cornice roof line is featured in most variants of this style.