The term "Mass" is derived from the concluding words of the Roman Rite Mass in Latin: "Ite, missa est" ("Go; it is the dismissal"). The Late Latin word missa substantively corresponds to the classical Latin word missio. In antiquity, missa simply meant "dismissal". In Christian usage, however, it gradually took on a deeper meaning. The word "dismissal" has come to imply a mission.
The following description of the celebration of Mass is limited to the current Ordinary Form of the Roman Rite, conducted using the local vernacular language and customs. This version was introduced in 1969 following calls for liturgical reforms by the bishops participating in the Second Vatican Council (1962–65) based on new historical perspectives and biblical studies, and has become the most common form used. This version was introduced to succeed the Tridentine Mass, celebrated in Latin and dating to the liturgical reforms of the Council of Trent (1545–46). The Tridentine Mass, as revised in 1962, is still permitted for use as an Extraordinary Form of the Roman Rite. Other historical and minor contemporary Latin Rite Masses have been used in different regions of the world, as well the Eastern Christian forms known as the Divine Liturgy.
The Catechism of the Catholic Church (CCC or Catechism) produced in 1994 discusses the importance of the Mass in the Catholic tradition based on the whole history of the Mass and the understanding of it to that time. The United States Catholic Conference edition of the Catechism prefers to call the Mass the “Eucharistic Celebration,” after its roots in the celebrational Last Supper. Under this topic in the Subject Index it lists as principal subtopics: commanded by Christ; center of the Church’s life; memorial celebration; in the Church from the beginning; participation as Church precept; structure and movement.
The Lectionary presents passages from the Bible arranged in the order for reading at each day's Mass. Compared with the scripture readings in the pre-1970 Missal, the modern Lectionary contains a much wider variety of passages, too many to include in the Missal. A Book of the Gospels, also called the Evangeliary, is recommended for the reading from the Gospels, but where this book is not available the Lectionary is used in its place.