Apse
In architecture, the
apse (Greek ἀψίς (apsis), then Latin
absis: "arch, vault"; sometimes written
apsis; plural
apsides) is a semicircular recess covered with a hemispherical vault or semi-dome, also known as an
Exedra. In Romanesque, Byzantine and Gothic Christian abbey, cathedral and church 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.