半圓形後殿

Also known as apsis

thumb|Typical early Christian Byzantine apse with a hemispherical semi-dome in the [[Basilica of Sant'Apollinare in Classe]] thumb|Typical floor plan of a cathedral, with the apse shaded In architecture, an apse (: apses; from Latin , 'arch, vault'; from Ancient Greek , , 'arch'; sometimes written apsis; : apsides) is a semicircular recess covered with a hemispherical vault or semi-dome, also known as an exedra. In Byzantine, Romanesque, and Gothic Christian church (including cathedral and abbey) architecture, the term is applied to a semi-circular or polygonal termination of the main building