aisle
Τhe part of the naos of a church set off by the internal rows of piers or columns, namely by the structures supporting the roof.

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.

basilica
In ancient Roman architecture a large oblong type building used as hall of justice and public meeting place. The roman basilica served as a model for early Christian churches.

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.

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

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.