apse
An arched srtucture or a semi-circular end of a wall. In byzantine architecture it means the semicircular, usually barrel-vaulted, niche at the east end of a basilica. The side aisles of a basilica may also end in an apse, but it is always in the central apse where the altar is placed. It was separated from the main church by a barrier, the templon, or the iconostasis. Its ground plan on the external side could be semicircular, rectangular or polygonal.

barrel-vault
vaulted, semi-cylindrical construction used often as roof.

bema
The area at east end of the naos in Byzantine churches, containing the altar, also referred to as the presbetery or hierateion (sanctuary). In these area take place the Holy Eucharist.

Christ Emmanuel (iconogr.)
An iconographic type of Christ, which shows him young and beardless, with a cross-halo. The youthful Christ is an image of the preexistent Logos who cannot be touched by time. This iconographic type, which recalls Early Christian portraits of Christ, appears in the 11th c. and becomes frequent under Manuel I Komnenos (1118-1180), who used it for his coinage.

cloisonné masonry
Masonry in which bricks are arranged vertically and horizontally, in single or double courses, around small stones or stone blocks, creating a colourful decorative effect.

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.

Deesis
Iconographic theme, an image of intercession for the salvation of the human race, which represents Jesus as the central figure, between the Virgin and St. John the Baptist

diakonikon
An auxiliary chamber of the church, also known in early years as skeuophylakion, which could be a separate building attached to the church. There were kept the sacred vessels but sometimes also the offerings of the faithful, the archive or library. In Byzantine churches the diakonikon becomes the sacristy to the south of the Bema, corresponding to the prothesis to the north, and forming along with them the triple sanctuary. It usually has an apse projecting to the east.

Greek cross-domed octagon
This type combines a centre bay in the shape of a domed octagon with the barrel- (or groin-) vaulted arms of a Greek cross, the whole enclosed in an outer square or rectangle. The resulting oblong corner-bays are used as chapels.

katholikon
The main church in a monastic complex, heart of the monastic activity.

narthex
A portico or a rectangular entrance-hall, parallel with the west end of an early Christian basilica or church.

prothesis
Ιn ecclesiastical architecture, the sacristy to the north of the sanctuary. Usually it has an apse projecting to the east. It is the chamber where the eucharistic elements were prepared (Proskomide) before the Communion.

rubble masonry
A building techinique that employs rough, unhewn stones of various size, set in mortar in irregular courses.

tympanum (lunette)
(Rom., Byz.) The arched panel (lunette) inside an arch or an arcosolium.