Plainsong or plainchant (calque from the French plain-chant; Latin: cantus planus) is a body of chants used in the liturgies of the Western Church. When referring to the term plainsong, it is those sacred pieces that are composed in Latin text. Plainsong was the exclusive form of Christian church music until the ninth century, and the introduction of polyphony. The monophonic chants of plainsong have a non-metric rhythm. Their rhythms are generally freer than the metered rhythm of later Western music, and they are sung without musical accompaniment.