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).

cistern
A receptacle for holding rainwater, but also water transported from elsewhere, in order to keep it stored. The cisterns were either covered eiter open, and they could have more than one compartements.

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.

drum of dome
Part of the church, semicircular or polygonal, on which rises an hemispheric dome

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.

mausoleum
A type of large-scale burial monument, named after the tomb of Mausolus, satrap of Caria.

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.

skeuophylax (megas)
A cleric, usually a priest, whose main duty was to look after the sacred valuables and liturgical vessels of a church.

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.