The formula of a prayer, "Lord, have mercy," said or sung and repeated in the penitential rite at the beginning of Mass in the Roman Liturgy. Used in conjunction with Christie Eleison, "Christ, have mercy." One of the few Greek prayers in the Latin Mass, it is most likely the remnant of a liturgical litany. It is also said in the Divine Office and in many litanies, notably the Litany of the Saints. In the Eastern Churches it may appear without Christie Eleison.