The Sacrifice of the Mass is divided into two parts: the Liturgy of the Word and the Liturgy of the Eucharist. Priests and certain members of religious congregations are required to pray the Liturgy of the Hours.
The Liturgical CalendarEdit
The Liturgical Year begins with the Season of Advent, followed by the Season of Christmas, followed by a period of Ordinary Time, followed by the Season of Lent, followed by the Easter Season, followed by another period of Ordinary Time which continues until the next Season of Advent. Select days of the year also commemorate specific Saints and the lives of Jesus and Mary.
Vessels and Vestments of the Mass and other CeremoniesEdit
The vestments used in the Mass are the amice (optional), alb, cincture, stole, and chasuble. The vessels used in the Mass are the primarily the paten and chalice. Other textile items also used are the purificator, chalice veil, corporal, and burse (optional). The cope and humeral veil are used in Eucharistic processions and Benediction. A deacon wears a dalmatic, rather than a chasuble. Acolytes either wear cassocks and surplices (or sometimes capes/humerales?), or they wear albs. Lectors, cantors, and choristers may occasionally wear vestments similar to those worn by acolytes. Important sanctuary furniture includes the tabernacle, altar(s), lectern, and ambo (optional). Other furniture in the church includes the baptismal font, sanctuary lamp, holy water fonts (optional), and pews.
The Order of the MassEdit
The Mass is begun with the Sign of the Cross and followed by the Penitential Rite. The Penitential Rite may have several different forms. It may be the Rite of Sprinkling, it may be the Confiteor (I Confess to Almighty God) followed by the Kyrie (Lord, have mercy), it may be the Kyrie combined with tropes (in this case, these tropes are usually statements about the different aspects of God), or it may be the simple Kyrie. For a few select days of the Liturgical Year (such as Ash Wednesday) a special rite proper to that day is substituted. The Gloria (Glory to God in the Highest) is recited Sunday Masses outside the Advent and Lenten Seasons,on solemnities, and on feasts. The Opening Prayer follows the Gloria (if the Gloria is omitted, it follows the Penitential Rite).
An excerpt from the Bible is read. During a weekday mass there are two readings and a psalm. The first reading is always from the Old Testament, except during the season of Easter, when it is from the Acts of the Apostles, and the second is from one of the Gospels. On Sundays and feastdays there are three readings. The first is always from the Old Testament, with the previous exception, and the second is from one of the New Testament epistles, with the third being the Gospel. The first reading is followed by a responsorial psalm (or a portion of it; the Responsorial Psalm may also be from a book of the Bible other than the Psalms), which is followed by the second reading (if there is one). On select days (such as Easter and Corpus Christi) there is a sequence. Then there is the Gospel Acclamation, followed by an excerpt from one of the four Gospels. A homily may follow this.
On solemnities and Sundays the Nicene Creed is prayed (for Masses with children the Apostles' Creed may be substituted). The General Intercessions conclude the Liturgy of the Word.
The Liturgy of the Eucharist begins with the Offertory. This is followed by the Prayer over the Gifts, the Preface to the Eucharistic Prayer, and the Sanctus (Holy, Holy). The priest may select from one of nine Eucharistic Prayers. Eucharistic Prayer I (also called the Roman Canon) is particularly suited to days when this Eucharistic Prayer has a special form (Christmas and Christmas Octave, Holy Thursday, Epiphany, Easter Vigil and Easter Octave, the Ascension, and Pentecost. Eucharistic Prayer II is particularly suitable for weekday Masses. Eucharistic Prayer III is particularly suitable for Sunday and holydays. Eucharistic Prayer IV recounts the history of salvation in greater detail and has a preface specifically assigned to it, and is suitable for days that are not assigned a preface.  There are also two reconciliatory Eucharistic Prayers, and three for Masses with children.
The Our Father is prayed, which, after several other prayers, may be followed by the optional Sign of Peace . The Agnus Dei (Lamb of God) is prayed or sung. The first two stanzas (?) may be repeated as many times as necessary until the ministers of the Eucharist are prepared, but the concluding stanza (?) always ends with grant us peace. The priest prays two inaudible prayers and, after the "This is the Lamb" and a prayer based on the statement of a centurion, the Eucharist is consumed by the priest and, in most cases, the faithful present who are in the state of grace and have prepared themselves by the prescribed fast.
The Prayer after Communion, followed by the Final Blessing, concludes the Mass.
The Liturgy of the HoursEdit
The Liturgy of the Hours, also known as the Divine Office, is prayed several times during the course of a day. The key parts of the Liturgy of the Hours are the Invitatory, Morning Prayer, Daytime Prayer, Evening Prayer, Night Prayer, and the Office of Readings. Clerics in the Roman Catholic Church are required by Canon Law to pray the major Hours of the Office, Morning and Evening Prayer; the daytime hours and the Office of Readings are optional. Generally, only monastic communities pray the full office every day.
The Invitatory begins the prayer of every day. It is composed of the verse "Lord, open my lips" with the response "And my mouth will proclaim your praise," followed by a psalm (usually Psalm 95, but it can be substituted with Psalm 100, 67, or 24). It is combined to the period of prayer which follows it, which may be either Morning Prayer or the Office of Readings.
Morning prayer is composed of the following: a hymn (unless Morning Prayer both follows and is combined with the Office of Readings, in which case the hymn proper to Morning Prayer is moved to the beginning of the Office of Readings),a psalm, an Old Testament canticle, a second psalm, a Biblical excerpt which serves as a reading, a responsory, the Canticle of Zechariah, a collection of intercessions, the Our Father, a concluding prayer, and the dismissal. LENT:Fasting , Absting etc.
Daytime prayer is composed of the following: a hymn, three psalms, a Biblical excerpt which serves as a reading, a responsory, a concluding prayer, and a final acclamation. Daytime Prayer can be a single period or three separate periods termed Midmorning, Midday, and Midafternoon.
Evening prayer is composed of the following: a hymn, two psalms, a New Testament canticle, a Biblical excerpt which serves as a reading, a responsory, the Canticle of Mary, a collection of intercessions, the Our Father, a concluding prayer, and the dismissal.
Night Prayer is composed of: an introduction, an examination of conscience, a penitential rite or prayer, a hymn or poem, one or two psalms, a Biblical excerpt which serves as a reading, a responsory, the Canticle of Simeon, a concluding prayer, and a Marian prayer.
The Office of ReadingsEdit
The Office of Readings is frequently combined with another period of prayer. It is composed of a hymn (it uses its own prescribed hymn if not combined to another period other than the invitatory, but it uses the hymn of the other period at its beginning if it is followed by and combined with another period), three psalms, a verse with a response, a Biblical reading, a responsory, a reading from one of the Church writers, a second responsory, the Te Deum (only recited on Sundays, solemnities, and feasts; maybe not during Lent and Advent?), a concluding prayer, and a final acclamation.
- General Instruction of the Roman Missal, #322
- The Sacramentary, page 563
- The Sacramentary, page 563