missal [Lat., = of the mass], in the Roman Catholic Church, liturgical book containing all directions and texts necessary for the performance of Mass throughout the year. The Roman Missal ( Missale Romanum ) published by Pope Pius V in 1570, over the years replaced the widespread use of separate missals by each diocese. A number of religious orders (e.g., the Dominicans) and certain privileged dioceses (e.g., Milan) still use missals containing elements proper to themselves. The missal is in Latin and vernacular forms. The Constitution on the Sacred Liturgy, issued by the Second Vatican Council in 1963, initiated a full-scale reform of the text of the Roman Missal.