ambulatory (byz. arch.)
A continuous passage that envelops the naos or the centrally planned core of a structure. In a cross-domed church, where the dome is supported on four masonry piers and between each pair of piers two columns are inserted, the ambulatory is formed by the lateral aisles and western part of the church. Later on, an ambulatory could also envelop a cross-in-square core. During the Palaeologan period, ambulatories, usually serving as funerary chambers, were added to many middle-Byzantine churches of Constantinople.

atrium
1. Antiquity: The large, open space within a building, which is envelopped by colonnades.2. Βyzantium: The forecourt of a church in early Christian, Byzantine, and medieval arcitecture. It was usually surrounded by four porticoes (quadriporticus).

chancel screen of presbytery
A short barrier between the bema and the nave. It had originally the form of a parapet that was later made of stone or of marble. It is generally an element of early Christian religious architecture, and it appears on ground plans either as a linear structure or forming a Π. It consists of small columns or pillars in the interspace of which slabs are inserted. Crosses and floral patterns are usually used for the relief decoration of the screen.

corner bays
In a cross-in-square church, they are the four compartements between the arms of the cross, that make inscribe the central cross into a square. They were usually covered with cross-or domical vaults.

cross-in-square church
Type of church in which four barrel-vaulted bays form a greek cross; the central square of their intersection is domed. The cross is inscribed into the square ground plan by means of four corner bays.

dome
A characteristic element of Byzantine architecture. The dome is a hemispherical vault on a circular wall (drum) usually pierced by windows. The domed church emerges in the Early Byzantine years and its various types gradually prevail, while they are expanded in the Balkans and in Russia.

gallery
The upper level of a house where the women resided. In ecclesiastical architecture it is the corridor above the aisles and narthex of a church, from where women attended the Liturgy. Originally (in the Byzantine period) the gallery, having a special entrance, was used exclusively by the emperor and the members of the royal family.

marble revetment
Τhe facing of a wall with slabs of marble

opus sectile, the
Technique of floor or wall decoration. Thin pieces of polychrome marble are carved or joined so that a decorative motif could be depicted.

synthronon
Rows of built benches, arranged in a semicircular tier like a theatre, in the apse of a church. On these benches the clergy sat during Divine Liturgy. The bishop sat on the cathedra at the top of the synthronon.

tzykanisterion
A stadium-like courtyard when the tzykanion was played; this was a ball game played on horseback (polo-like), imported from Persia (Pers. tshu-qan).

vault
A semi-cylindrical roof.