1. (n.) A projecting part of a building, esp. of a church, having in the plan a polygonal or semicircular termination, and, most often, projecting from the east end. In early churches the Eastern apse was occupied by seats for the bishop and clergy.

2. (n.) The bishop's seat or throne, in ancient churches.

3. (n.) A reliquary, or case in which the relics of saints were kept.

Easter sepulcher ambry arcade arcature arch arched roof archway baptistery blindstory camber ceilinged roof chancel choir cloisters concameration concha confessional confessionary cove crypt cupola diaconicon diaconicum dome geodesic dome igloo keystone nave ogive porch presbytery rood loft rood stair rood tower sacrarium sacristy skewback span transept triforium vault vaulting vestry voussoir