:''This article is about an architectural feature; for the astronomical term see
apsis. For the rock band, see
Apse (band). Or you may mean the acronym
APS.''
In
architecture, the 'apse' (
Latin ''absis'' "arch, vault"; sometimes written ''apsis''; plural ''apses'') is a semicircular recess covered with a hemispherical
vault. In
Romanesque,
Byzantine and
Gothic Christian
abbey,
cathedral and
church architecture, the term is applied to the semi-circular or polygonal section of the sanctuary at the liturgical east end beyond the
altar. Geometrically speaking, an apse is either a half-cone or half-dome.
Definition
The epithet "apsidal" may be applied to the
exedra of
classical architecture, a feature of the secular Roman
basilica, which provided some prototypes for Early Christian churches. The apse in the Roman basilica was often raised (as the sanctuary generally still is) as a hieratic feature that set apart the magistrates who deliberated within it.

A simple apse set into the east end of an English parish church, at
Poulton-le-Fylde, Lancashire.

Fresco within the apse of an Orthodox church.
The apse as a semicircular projection (which may be polygonal on the exterior, or reveal the radiating projections of
chapels) may be roofed with a half-dome or with radiating
vaulting. A simple apse may be merely embedded within the wall of the east end. Eastern orthodox churches may have a triple apse, which is usually a mark of
Byzantine influence when it is seen in Western churches.

The triple apse of an Orthodox church.

East end of the abbey church of Saint-Ouen, showing the ''chevet''), Rouen,
Seine-Maritime.
Smaller subsidiary apses may be found around the choir or even at the ends of
transepts. An exedra or apse may be reduced in scale to form a
niche within the thickness of walling; a niche does not reveal its presence by projecting on the exterior. Where an apse contains an altar or throne it can be architecturally referred to as a
tribune.
The interior of the apse is traditionally a focus of
iconography, bearing the richest concentration of
mosaics, or painting and sculpture, towards which all other decoration may tend.
Parts of the apse
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:
Presbytery
In the 'presbytery' or 'sanctuary' directly to the east beyond the
choir is the High Altar, where there is one (compare
communion table). This area is reserved for the clergy. The word derives from the
Greek ''presbuteros'' meaning "
elder".
Choir or Quire
According to the ''
Concise Oxford Dictionary'', the word `choir` in an architectural context means the part of a church `between the altar and the
nave`, used by the church choir.
Chancel
The word "chancel" derives from the French usage of ''chancel'' from a
Late Latin word ''cancelli'' meaning "lattice" (
Online Etymology Dictionary). The grating in question separated the chancel from the
nave, thus "chancel" refers to the part of a church near the main altar used by the priests and open to the choir.
Chevet
In the beginning of the 13th century in France, the apses were built as radiating chapels outside the choir aisle, henceforth known as the ''chevet'' (French, "headpiece"), when the resulting structure was too complicated to be merely an "apse". Famous northern French examples of chevets are in the Gothic cathedrals of
Amiens,
Beauvais and
Reims. Such radiating chapels are found in England in
Norwich and
Canterbury cathedrals, but the fully-developed feature is essentially French, though the Francophile connoisseur
Henry III introduced it into
Westminster Abbey.
Ambulatory
The word "ambulatory" refers to a curving
aisle in the apse that passes behind the choir, giving access to chapels in the chevet. An "ambulatory" ("walking space") may refer to the arcaded passages that enclose a
cloister in a
monastery.
See also
★
Cathedral architecture
★
Byzantine architecture
★
Narthex
★
Church architecture
★
Cathedral architecture of Western Europe
★
Chancel repair liability in the
United Kingdom