[D]ado: the surface of an interior wall, between the base moulding and an upper moulding, placed some distance from the ceiling.
Decastyle: See Portico.
Decorated: used to distinguish the second period of English Gothic (fourteenth century), owing to increased richness of window traceries and other ornamentation. Compare Rayonnant.
Dentil: one of a series of square, so-called tooth-like, blocks that ornament the cornice in the Ionic and Corinthian Orders.
Diagonal: specifically applied to the arches or ribs of a vaulting that are diagonal to the main axis. Compare Longitudinal, Transverse.
Dipteral (lit. “double-winged”): designating a temple that has a double range of columns on each side of the cella. Compare Pseudo-dipteral.
Dolmen: a prehistoric megalithic monument, composed of single stones set on end or on edge and crowned with a single slab; forming a sepulchral chamber, often embedded in a mound. See Mastaba.
Dome: a spherical roof, over a circular, square or polygonal space rising like an inverted cup. Hence, when the structure is small, called a Cupola.
Doric: the earliest and simplest Order (which see) of architecture developed on the mainland of Hellas.
Dormer (lit. “sleeping”): a window in a roof, usually of a bedroom, often projecting with a gable end.