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.

arcosolium
(lat.) A tomb carved out of a wall (solium) with an arched niche (arcus) above it.

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.

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.

exonarthex (outer narthex)
The transverse vestibule or portico preceding the narthex of the church.

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

megas logothetes
The head of the civil Byzantine administration. Megas logothetes was a title used at the end of the 12th century during the reign of Isaac II Angelos (1185-1195), replacing the “logothetes ton sekreton”, an office which was created during the reign of Alexios I Komnenos (1081-1118) to bring the entire civil administration under the control of a single individual.

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

opus reticulatum (lat.)
1. Roman masonry in which the external facade of concrete-built walls is covered with diamond-shaped bricks or stones in an arrangemend that resembles a net.2. Decorative brick pattern on the exterior walls of Middle- and Late Byzantine churches, where diamond-shaped tiles are arranged in a similar way, usually on the lunettes of arched niches.

protostrator
A Byzantine military office, accorded to the chief of imperial stratores or hippokomoi («grooms»). The title is first mentionned in the 8th century. In the 9th and 10th century, his major duty was to accompany the Emperor while on horseback. In the 12th century he was one of the highest officials of the Byzantine court and he also commanded troops.

trochilus (or scotia)
An annular moulding whose section is concave, usually at the base of an ionic column, between two tori (sing.: torus), the large convex moldings at the base of the column.