Latin: apsis, arch
Semicircular or polygonal termination to the choir or aisles of a church, in which the altar was placed; so called from being vaulted. The term may be applied to the canopy over the altar; a dome; the arched roof of a room; the bishop‘s seat; a reliquary; a semicircular recess with a roof. The apse is always solid below, generally with windows above. The chevet is an apse enclosed by an open screen of columns, opening into an aisle, then into three or more apsidal chapels. The term was first used in reference to a Roman basilica, of which the apse was an important feature and was retained after the basilica was transformed into the Christian Church. It was retained in Byzantine churches, was universally adopted in Germany, and was common in France and Italy. England preferred the square termination. In the larger Gothic churches of France the apse is polygonal and becomes the chevet, with its radial chapels.