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odeon, odeion (Greek)

Roofed building (theatre) for musical performances or recitations in Ancient Greece and Rome with tiered seats for the spectators organised concentrically to the stage.

oikos (Greek)

A space for dining with its widest side open to the peristyle of the house.

opus (Latin)

Latin for work, as intended to designate construction, or arrangement of materials in construction - for example different ways of masonry, decorative finishing of walls and floors, specific to the Roman building techniques.

opus tessellatum (Latin)

Pavement or facing of regular shaped pieces of different material and colours forming geometrical patterns usually used to form the background of a mosaic.

opus vermiculatum (Latin)

A type of mosaic with tesserae laid in curving lines usually outlining shapes and figures.

orchestra, orchaestra (Greek)

Central space in the classical Greek theatre between the theatron and the proskenion. Its original form in the Ancient Greek theatres was full circle, and in Roman ones - semicircle. Typical for the Roman Empire provinces are the orchestras in the form of a horseshoe.


Structural and aesthetic interdependence of the architectural systems - post-and-lintel system or arch-and-vault system.

orthostat, orthostata, pl. orthostatae (Greek)

One of several large stone slabs set vertically in the base of a stone masonry wall to form part of the facing.

ostium (Latin)

The entrance to houses in Ancient Rome.