Lectionaries are books containing biblical scripture readings used during religious services. There are several synonyms for lectionaries, including missals, service books, liturgical books, and sacramentaries. A missal is a book used during Catholic Mass that contains the prayers and readings for the entire liturgical year. Service books are used in many Christian denominations and contain scripture readings, prayers, and hymns for each Sunday and holiday throughout the year. Liturgical books are produced by publishers to enable the people to follow the liturgy, and sacramentaries are collections of ecclesiastical texts used in the Catholic Church for the celebration of the sacraments. Whatever the name, these books serve an essential role in the worship of many faith communities.