Apse

In architecture, an apse (from Latin absis: "arch, vault" from Greek ἀψίς apsis "arch"; sometimes written apsis; plural apsides) is a semicircular recess covered with a hemispherical vault or semi-dome, also known as an Exedra. 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. Smaller apses may also be in other locations, especially shrines.

An apse is a semicircular recess covered with a hemispherical vault. 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. In relation to church architecture it is generally the name given to where the altar is placed or where the clergy are seated. An apse is occasionally found in a synagogue, e.g. Maoz Haim Synagogue.

The apse is separated from the main part of the church by the transept.

Smaller apses are sometimes built in locations other than the east end, especially for reliquaries or shrines of saints.

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

In the Eastern Orthodox tradition, the south apse is known as diaconicon and the north apse as prothesis. Various ecclesiastical features of which the apse may form part are drawn together here:

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