INDIANA LIMESTONE -- a fine-grain limestone rock quarried in Indiana.

INTAGLIO -- a decorative figure engraved or incised in a hard material such as stone.

IONIC -- a classical architectural order characterized by fluted columns with spiral volutes in the capitals.

ITALIANATE -- a popular mid -1880's architectural style with wide, heavily bracketed eaves over a nearly square structure and usually a low-pitched hip roof with a cupola.

JALOUSIE -- a window or door made of adjustable glass louvers that control ventilation.

JAMB -- the upright side of a window or door opening, against which the sash or door abuts.

JERKINHEAD ROOF -- a roof with a clipped gable, a gable cut off by a secondary slope forming a hip.

JETTY -- a structure extending into a body of water to influence the current or tide.

JIG SAW -- a machine saw with a narrow vertically reciprocating blade for cutting curved and irregular lines.

JOINT -- in masonry, the interstice between two bricks or stones.

JOIST -- a horizontal member in the framing of a floor or ceiling.

KEYSTONE -- a wedge-shaped piece at the crown of an arch that locks the other members in place.

LANCET ARCH -- a sharply pointed slender arch, commonly used in Gothic architecture.

LANDING -- a horizontal platform on a stairway.

LANTERN -- a small circular or polygonal turret with windows all around, crowning a roof, dome, or tower.

LATTICE WINDOW -- a window with diamond shaped panes, whose diagonal muntins have a decorative effect.

LEADED GLASS -- ornamental glass panes set in lead division strips.

LIGHT -- a panel of glass (in a window or door).

LINENFOLD -- carved wood decoration simulating a piece of linen folded vertically, common in Tudor  paneling.

LINTEL -- a horizontal beam or stone that spans an opening.

LOGGIA -- a passage or gallery, colonnaded on one or both sides.

LOUVER -- one of a series of slanted panels, usually of wood or glass, that allows ventilation but excludes rain.

LOZENGE -- a diamond shape.

LUNETTE -- a round or semicircular window opening in a vaulted ceiling.