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 (of which there would have been little if any in the Middle Ages). 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.
As an architectural term "choir" remains distinct from the actual location of any singing choir – these may located in various places, and often sing from a choir-loft, often over the door at the liturgical western end. In modern churches, the choir may be located centrally behind the altar, or the pulpit.
The back-choir or retro-choir is a space behind the high altar in the choir of a church, in which there may be a small altar standing back to back with the other.
In the Early Church, the sanctuary was connected directly to the nave. The choir was simply the east part of the nave, and was fenced off by a screen or low railing, called cancelli, which is where the English word chancel comes from. The development of the architectural feature known as the choir is the result of the liturgical development brought about by the end of persecutions under Constantine the Great and the rise of monasticism. The word "choir" is first used by members of the Latin Church. Isidore of Seville and Honorius of Autun write that the term is derived from the "corona", the circle of clergy or singers who surrounded the altar.