the Gregorian chant (q.v.) and, by extension, other similar religious chants. The word derives from the 13th-century Latin term cantus planus (“plain song”), referring to the unmeasured rhythm and monophony (single line of melody) of Gregorian chant, as distinguished from the measured rhythm of polyphonic (multipart) music, called cantus mensuratus, or cantus figuratus (“measured,” or “figured,” song). Its other main application is to ancient Christian music with the same unmeasured rhythm and monophony—in the West, Ambrosian (Ambrosian chant), Gallican (Gallican chant), and Mozarabic (Mozarabic chant) chants (qq.v.); in the East, Byzantine (Byzantine chant), Syrian (Syrian chant), Coptic (Coptic chant), Ethiopian (Ethiopian chant), and Armenian (Armenian chant) chants (qq.v.). It may also refer to similar non-Christian religious music, such as Jewish and Hindu chants.