A choir, also sometimes called quire, is the area of a church or cathedral that provides seating for the clergy and church choir. It is in the western part of the chancel, between the nave and the sanctuary, which houses the altar and Church tabernacle. In larger medieval churches it contained choir-stalls, seating aligned with the side of the church, so at right-angles to the seating for the congregation in the nave. Smaller medieval churches may not have a choir in the architectural sense at all, and they are often lacking in churches built by all denominations after the Protestant Reformation, though the Gothic Revival revived them as a distinct feature.

In architecture, an apse is a semicircular recess covered with a hemispherical vault or semi-dome, also known as an exedra. In Byzantine, Romanesque, and Gothic Christian church architecture, the term is applied to a semi-circular or polygonal termination of the main building at the liturgical east end, regardless of the shape of the roof, which may be flat, sloping, domed, or hemispherical. Smaller apses are found elsewhere, especially in shrines.