The shape or appearance of an object. The convenience form is the additional modification necessary to a cavity in order to gain access to it or to insert a restoration. The occlusal form is the shape of the biting surface of a tooth. The outline form is the shape of a cavity defined by the cavosurface outline of the cavity. The resistance form is the shape given to a prepared cavity to enable the restoration to withstand displacement due to masticatory forces. The retention form is the shape of a prepared cavity designed to prevent displacement of a restoration in a direction opposed to masticatory forces.