Apse

Etymology
Via apsis:, from  ἁψίς:, from ἅπτω:.

Pronunciation

 * , {{SAMPA|/{ps/}}

Noun

 * 1)  A semicircular projection from a building, especially the rounded east end of a church that contains the altar.
 * 2)  The nearest and furthest points to the centre of gravitational attraction for a body in orbit.  More usually called an apsis.
 * 3)  In some local dialects and in archaic usage, an aspen tree.

Thesaurus
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