Euchology, also known as a sacramentary or missal, refers to a liturgical book containing the prayers and rituals used in the celebration of the Eucharist or mass. Synonyms for Euchology include liturgical book, sacramentary, missal, ritual book, or mass book. These books are usually used by priests and other religious officials to guide them through the various prayers and actions that take place during the Eucharist. In addition to prayers, a Euchology may also include hymns, readings, and other liturgical elements necessary for the celebration of the sacrament. These synonyms refer to the same essential book and are often used interchangeably.