Glossary of Architecture - O

O

Oillets

Arrow slits in the walls of medieval fortifications, but more strictly applied to the round hole or circle with which the openings terminate. The same term is applied to the small circles inserted in the tracery-head of the windows of the Decorated and Perpendicular periods, sometimes varied with trefoils and quatrefoils.

Order

An order refers to each of a series of mouldings most often found in Romanesque and Gothic arches.

Orthostatae

(Greek: ὀρθοστάτης, standing upright) - Greek architecture term for the lowest course of masonry of the external walls of the naos or cella, consisting of vertical slabs of stone or marble equal in height to two or three of the horizontal courses which constitute the inner part of the wall.

Orthostyle

(Greek: ὃρθος, straight, and στῦλος, a column) - a range of columns placed in a straight row, as for instance those of the portico or flanks of a classic temple.