Apse

In architecture, the apse (from Latin apsis: "arch, vault") is a semicircular recess covered with a hemispherical vault or semi-dome.Lilian H. Zirpolo, Historical Dictionary of Baroque Art and Architecture (Lanham, MD: Scarecrow Press, 2010), p. 71 It is similar to another form known as an exedra.William Audsley, Popular Dictionary of Architecture and the Allied Arts, Vol 3 (New York: G.P. Putnam's Sons, 1882), p. 77, note † In Romanesque, Byzantine and Gothic Christian abbey, cathedral and church architecture, the term is applied to a semi-circular or polygonal termination of the main building. This is usually at the liturgical east end (where the altar is). It is also regardless of the shape of the roof, which may be flat, sloping, domed, or hemispherical.

 References 

Category:Architectural elements