- 1: an organized company of singers (as in a church service)
- 2: a group of instruments of the same class <a brass choir>
- 3: an organized group of persons or things
- 4: a division of angels
- 5: the part of a church occupied by the singers or by the clergy; also : the part of a church where the services are performed
- 6: a group organized for ensemble speaking
A body of singers who perform together as a group is called a choir or chorus. The former term is very often applied to groups affiliated with a church (whether or not they actually occupy the choir) and the second to groups that perform in theatres or concert halls, but this distinction is far from rigid.
The term "Choir" has the secondary definition of a subset of an ensemble; thus one speaks of the "woodwind choir" of an orchestra, or different "choirs" of voices and/or instruments in a polychoral composition. In typical 18th- to 21st-century oratorios and masses, chorus or choir is usually understood to imply more than one singer per part, in contrast to the quartet of soloists also featured in these works.
The origins of choral music are found in traditional music, as singing in big groups is extremely widely spread in traditional cultures (both singing in one part, or in unison, like in Ancient Greece, as well as singing in parts, or in harmony, like in contemporary European choral music).
The oldest unambiguously choral repertory that survives is that of ancient Greece, of which the 2nd century BC Delphic hymns and the 2nd century AD. hymns of Mesomedes are the most complete. The original Greek chorus sang its part in Greek drama, and fragments of works by Euripides (Orestes) and Sophocles (Ajax) are known from papyri. The Seikilos epitaph (2c BC) is a complete song (although possibly for solo voice). One of the latest examples, Oxyrhynchus hymn (3c) is also of interest as the earliest Christian music.