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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.

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.

client (lat. cliens)
In the Roman and Late Roman history the 'cliens' was a man (or sometimes a foreign state) who, for any of a number of reasons, puts himself under the protection and sponsorship of a patron benefactor ("patronus")

koubikoularios or cubicularius
(from lat. cubicularius) The term designated eunuch officials in the service of the Emperor. Apart from their particular responsibilities in the court, they oftenly held positions as military commanders and undertook diplomatic delegations.

praepositos
(from lat. praepositus sacri cubiculi) The praepositos or praipositos (πραιπόσιτος του ιερού κουβουκλίου or του ευσεβεστάτου κοιτώνος) was a grand chamberlain by the Early Byzantine period the highest official, usually Eunuch, in the imperial service. After the 6th C. his functions were assumed by the parakoimomenos. The dignity involved in palace ceremony and disappeared until the end of 11th C.

triclinium
Hall for symposia where three anaklintra were placed around the three sides of a square table. During the Late Roman period it was the main reception area of both houses and palaces (the term is maintained in the Byzantine era).