Apse

In Byzantine, Romanesque, and Gothic Christian church (including cathedral and abbey) architecture, the term is applied to a semi-circular or polygonal termination of the main building at the liturgical east end (where the altar is), regardless of the shape of the roof, which may be flat, sloping, domed, or hemispherical.

Commonly, the apse of a church, cathedral or basilica is the semicircular or polygonal termination to the choir or sanctuary, or sometimes at the end of an aisle.

[citation needed] The domed apse became a standard part of the church plan in the early Christian era.

The chancel (or sanctuary), directly to the east beyond the choir, contains the high altar, where there is one (compare communion table).

This area is reserved for the clergy, and was therefore formerly called the "presbytery", from Greek presbuteros, "elder", [citation needed] or in older and Catholic usage "priest".