- Architecture. a semicircular or polygonal termination or recess in a building, usually vaulted and used especially at the end of a choir in a church.
- Astronomy. an apsis.
- Also called: apsis a domed or vaulted semicircular or polygonal recess, esp at the east end of a church
- astronomy another name for
“semicircular extension at the end of a church,” 1846, from Latin apsis “an arch, a vault,” from Greek hapsis (Ionic apsis) “loop, arch,” originally “a fastening, felloe of a wheel,” from haptein “fasten together,” of unknown origin. The original sense in Greek seems to have been the joining of the arcs to form a circle, especially in making a wheel. The architectural term is earlier attested in English in the Latin form (1706).