Apse

Apse, recess in a building, generally a semicircular or polygonal projection from the exterior of a church, roofed with a vault. The word 'apse' is derived from the Latin word 'apsis', which is in turn derived from the Greek word '(h)apsis', meaning 'arch', or 'vault'. The apse was originally a niche in a Roman temple, intended to hold a statue of a god. Later it was the portion of a rectangular, aisled basilica that contained the presiding official's chair. Carried over into Early Christian church architecture, which adapted the basilica form, it customarily occupied the east end of the church, where the altar stood. The apse continued in Romanesque and Gothic churches at the east end of the nave and sometimes at the ends of the transepts as well.