The noun chorus (from the Greek χορός‚ 'choros') originally meant 'a dance', and by extension 'the group of dancers', who could also be singers. The precursor of Greek tragedy was performances of the kind of choral lyric known as the dithyramb, sung and danced in honour of the god Dionysus, in competition at the Dionysia. Such dithyrambic choruses (of about 50 members) did not wear masks; they danced and sang in a circle in the orchestra.
In Greek tragedy, the chorus, numbering twelve or fifteen, was always 'in role', i.e., it represented a group which bore some relation to the main characters in the tragedy, and its function was to comment on the action of the drama. The chorus often sang and danced in unison, but it could also divide into semi-choruses and engage in statement and refrain, exposition and response, or even dialogue. (There were also choruses in the satyr-plays, where the Chorus numbered 12 even after Sophocles had instituted 15 as the standard number in the tragedies, and Old comedy with 24.) The Greek chorus usually communicated in song form, but sometimes spoke their lines in unison, and with the aid of dance and exaggerated gesture helped to expound the play to the huge audience in the outdoor theatres of Greece.
before the development of the protagonist and other actors in the sixth century BCE,
On the Elizabethan stage the Chorus was the speaker of an introductory prologue, a legacy from Euripides handed down via the Roman closet dramas of Seneca. He spoke either at the beginning of the play, as in Henry VIII, or before two or more acts, as in Romeo and Juliet, Henry V, and, in the person of Gower, in Pericles Prince of Tyre.
In the late 19th-century English theatre the chorus was the troupe of supporting singers and dancers. They had always accompanied the principal actors in burlesque, extravaganza, and pantomime, but it was not until about 1870 that the 'chorus girl' became a player in her own right. At first she was asked to do no more than wear lovely clothes and move gracefully in unison with her companions, often accompanied by handsome but fairly static 'chorus boys'. By the 1920s chorus girls were wearing fewer clothes and reached a high standard of precision dancing. The men were often dispensed with at this time, but after the Second World War, under the influence of the American musical, the chorus, both men and women, often took a much larger share in the plot.