Chapter II-C. Individual Parts of the Mass
a. Introductory Rites
24. The parts preceding the Liturgy of the Word, namely, the entrance song, greeting, penitential rite, Kyrie, Gloria, and opening prayer or collect, have the character of a beginning, introduction, and preparation.
The purpose of these rites is that the faithful coming together take on the form of a community and prepare themselves to listen to God's word and celebrate the Eucharist properly.
25. After the people have assembled, the entrance song begins as the priest and the ministers come in. The purpose of this song is to open the celebration, intensify the unity of the gathered people, lead their thoughts to the mystery of the season or feast, and accompany the procession of priest and ministers.
26. The entrance song is sung alternately either by the choir and the congregation or by the cantor and the congregation; or it is sung entirely by the congregation or by the choir alone. The antiphon and psalm of the Graduale Romanum or The Simple Gradual may be used or another song that is suited to this part of the Mass, the day, or the season and that has a text approved by the conference of bishops.
If there is no singing for the entrance, the antiphon in the Missal is recited either by the faithful, by some of them, or by a reader; otherwise it is recited by the priest after the greeting.
Veneration of the Altar and Greeting the Congregation
27. When the priest and the ministers enter the sanctuary, they reverence the altar. As a sign of veneration, the priest and deacon kiss the altar; when the occasion warrants, the priest may also incense the altar.
28. After the entrance song, the priest and the whole assembly make the sign of the cross. Then through his greeting the priest declares to the assembled community that the Lord is present. This greeting and the congregation's response express the mystery of the gathered Church.
29. After greeting the congregation, the priest or other qualified minsters may very briefly introduce the faithful to the Mass of the day. Then the priest invites them to take part in the penitential rite, which the entire community carries out through a communal confession and which the priest's absolution brings to an end.
30. The the Kyrie begins, unless it has already been included as part of the penitential rite. Since it is a song by which the faithful praise the Lord and implore His mercy, it is ordinarily prayed by al, that is, alternately by the congregation and the choir or cantor.
As a rule each of the acclamations is said twice, but, because of the idiom of different languages, the music, or other circumstances, it may be said more than twice or a short verse (trope) may be interpolated. If the Kyrie is not sung, it is to be recited.
31. The Gloria is an ancient hymn in which the Church, assembled in the Holy Spirit, praises and entreats the Father and the Lamb. It is sung by the congregation, or by the congregation alternately with the choir, or by the choir alone. If not sung, it is to be recited either by all together or in alternation.
The Gloria is sung or said on Sundays outside of Advent and Lent, on solemnities and feasts, and in special, more solemn celebrations.
Opening Prayer or Collect
32. Next the priest invites the people to pray and together with him they observe a brief silence so that they may realize they are in God's presence and may call their petitions to mind. The priest then says the opening prayer, which custom has named the "collect." This expresses the theme of the celebration and the priest's words address a petition to God the Father through Christ in the Holy Spirit.
The people make the prayer their own and give their assent by the acclamation, Amen.
In the Mass only one opening prayer is said; this rule applies also to the prayer over the gifts and the prayer after communion.
The opening prayer ends with the longer conclusion, namely:
- if the prayer is directed to the Father: We ask this (Grant this) through our Lord Jesus Christ, Your Son, who lives and reigns with You and the Holy Spirit, one God, for ever and ever;
- if it is directed to the Father, but the Son is mentioned at the end: Who lives and reigns with You and the Holy Spirit, one God, for ever and ever;
- if directed to the Son: You live and reign with the Father and the Holy Spirit, one God, for ever and ever.
The prayer over the gifts and the prayer after communion end with the shorter conclusion, namely:
- if the prayer is directed to the Father: We ask this (Grant this) through Christ our Lord;
- if it is directed to the Father, but the Son is mentioned at the end: Who lives and reigns with You for ever and ever;
- if it is directed to the Son: You live and reign for ever and ever.
b. Liturgy of the Word
33. Readings from Scripture and the chants between the readings form the main part of the Liturgy of the Word. The homily, profession of faith, and general intercessions or prayer of the faithful expand and complete this part of the Mass. In the readings, explained by the homily, God is speaking to His people,  opening up to them the mystery of redemption and salvation, and nourishing their spirit; Christ is present to the faithful through His own word.  Through the chants the people make God's word their own and through the profession of faith affirm their adherence to it. Finally, having been fed by the word, they make their petitions in the general intercessions for the needs of the Church and for the salvation of the whole world.
34. The readings lay the table of God's word for the faithful and open up the riches of the Bible to them.  Since by tradition the reading of the Scriptures is a ministerial, not a presidential function, it is proper that as a rule a deacon or, in his absence, a priest other than the one presiding read the gospel. A reader proclaims the other readings. In the absence of a deacon or another priest, the celebrant reads the gospel. 
35. The liturgy itself inculcates the great reverence to be shown toward the reading of the gospel, setting it off from the other readings by special marks of honor. A special minister is appointed to proclaim it and prepares himself by a blessing or prayer. The people, who by their acclamations acknowledge and confess Christ present and speaking to them, stand as they listen to it. Marks of reverence are given to the Book of the Gospels itself.
Chants Between the Readings
36. After the first reading comes the responsorial psalm or gradual, an integral part of the Liturgy of the Word. The psalm as a rule is drawn from the Lectionary because the individual psalm texts are directly connected with the individual readings: the choice of psalm depends therefore on the readings. Nevertheless, in order that the people may be able to join in the responsorial psalm more readily, some texts of responses and psalms have been chosen, according to the different seasons of the year and classes of saints, for optional use, whenever the psalm is sung, in place of the text corresponding to the reading.
The psalmist or cantor of the psalm sings the verses of the psalm at the lectern or other suitable place. The people remain seated and listen, but also as a rule take part by singing the response, except when the psalm is sung straight through without the response.
The psalm when sung may be either the psalm assigned in the Lectionary or the gradual from the Graduale Romanum or the responsorial psalm or the psalm with Alleluia as the response from The Simple Gradual in the form they have in those books.
37. As the season requires, the Alleluia or another chant follows the second reading.
a)The Alleluia is sung in every season outside Lent. It is begun either by all present or by the choir or cantor; it may then be repeated. The verses are taken from the Lectionary or the Graduale.
b)The other chant consists of the verse before the gospel or another psalm or tract, as found in the Lectionary or the Graduale.
38. When there is only one reading before the gospel:
a)during a season calling for the Alleluia, there is an option to use either the psalm with Alleluia as the response, or the responsorial psalm and the Alleluia with its verse, or just the psalm, or just the Alleluia.
b)during the season when the Alleluia is not sung, it is to be recited. If not sung, the Alleluia or the verse before the gospel may be omitted.
40. Sequences are optional, except on Easter Sunday and Pentecost.
41. The homily is an integral part of the liturgy and is strongly recommended:  it is necessary for the nurturing of the Christian life. It should develop some point of the readings or of another text from the Ordinary or from the Proper of the Mass of the day, and take into account the mystery being celebrated and the needs proper to the listeners. 
42. There must be a homily on Sundays and holydays of obligation at all Masses that are celebrated with a congregation; it may not be omitted without a serious reason. It is recommended on other days, especially on the weekdays of Advent, Lent, and the Easter season, as well as on other feasts and occasions when the people come to church in large numbers. 
The homily should ordinarily be given by the priest celebrant.
Profession of Faith
43. The symbol or profession of faith in the celebration of Mass serves as a way for the people to respond and to give their assent to the word of God heard in the readings and through the homily and for them to call to mind the truths of faith before they begin to celebrate the Eucharist.
44. Recitation of the profession of faith by the priest together with the people is obligatory on Sundays and solemnities. It may be said also at special, more solemn celebrations.
If it is sung, as a rule all are to sing it together or in alternation.
45. In the general intercessions or prayer of the faithful, the people, exercising their priestly function, intercede for all humanity. It is appropriate that this prayer be included in all Masses celebrated with a congregation, so that petitions will be offered for the Church, for civil authorities, for those oppressed by various needs, for all people, and for the salvation of the world. 
46. As a rule the sequence of intentions is to be:
a)for the needs of the Church;
b)for public authorities and the salvation of the world;
c)for those oppressed by any need;
d)for the local community.
In particular celebrations, such as confirmations, marriages, funerals, etc., the series of intercessions may refer more specifically to the occasion.
47. It belongs to the priest celebrant to direct the general intercessions, by means of a brief introduction to invite the congregation to pray, and after the intercessions to say the concluding prayer. It is desirable that a deacon, cantor, or other person announce the intentions.  The whole assembly gives expression to its supplication either by a response said together after each intention or by silent prayer.
c. Liturgy of the Eucharist
48. At the last supper Christ instituted the sacrifice and paschal meal that make the sacrifice of the cross to be continuously present in the Church, when the priest, representing Christ the Lord, carries out what the Lord did and handed over to His disciples to do in His memory. 
Christ took the bread and the cup and gave thanks; He broke the bread and gave it to His disciples, saying: "Take and eat, this is my body." Giving the cup, He said: "Take and drink, this is the cup of my blood. Do this in memory of me." Accordingly, the Church has planned the celebration of the eucharistic liturgy around the parts corresponding to these words and actions of Christ:
1) In the preparation of the gifts, the bread and the wine with water are brought to the altar, that is, the same elements that Christ used.
2) In the eucharistic prayer thanks is given to God for the whole work of salvation and the gifts of bread and wine become the body and blood of Christ.
3) Through the breaking of the one bread the unity of the faithful is expressed and through communion they receive the Lord's body and blood in the same way the apostles received them from Christ's own hands.
Preparation of the Gifts
49. At the beginning of the Liturgy of the Eucharist the gifts, which will become Christ's body and blood, are brought to the altar.
First the altar, the Lord's table, which is the center of the whole eucharistic liturgy,  is prepared: the corporal, purificator, missal, and chalice are placed on it (unless the chalice is prepared at a side table).
The gifts are then brought forward. It is desirable for the faithful to present the bread and wine, which are accepted by the priest or deacon at a convenient place. The gifts are placed on the altar to the accompaniment of the prescribed texts. Even though the faithful no longer, as in the past, bring the bread and wine for the liturgy from their homes, the rite of carrying up the gifts retains the same spiritual value and meaning.
This is also the time to receive money or other gifts for the church or the poor brought by the faithful or collected at the Mass. These are to be put in a suitable place but not on the altar.
50. The procession bringing up the gifts is accompanied by the presentation song, which continues at least until the gifts have been placed on the altar. The rules for this song are the same as those for the entrance song (no. 26). If it is not sung, the presentation antiphon is omitted.
51. The gifts on the altar and the altar itself may be incensed. This is a symbol of the Church's offering and prayer going up to God. Afterward the deacon or other minister may incense the priest and the people.
52. The priest then washes his hands as an expression of his desire to be cleansed within.
53. Once the gifts have been placed on the altar and the accompanying rites completed, the preparation of the gifts comes to an end through the invitation to pray with the priest and the prayer over the gifts, which are a preparation for the eucharistic prayer.
54. Now the center and summit of the entire celebration begins: the eucharistic prayer, a prayer of thanksgiving and sanctification. The priest invites the people to lift up their hearts to the Lord in prayer and thanks; he unites them with himself in the prayer he addresses in their name to the Father through Jesus Christ. The meaning of the prayer is that the entire congregation joins itself to Christ in acknowledging the great things God has done and in offering the sacrifice.
55. The chief elements making up the eucharistic prayer are these:
a) Thanksgiving (expressed especially in the preface): in the name of the entire people of God, the priest praises the Father and gives thanks to Him for the whole work of salvation or for some special aspect of it that corresponds to the day, feast, or season.
b) Acclamation: joining with the angels, the congregation sings or recites the Sanctus. This acclamation is an intrinsic part of the eucharistic prayer and all the people join with the priest in singing or reciting it.
c) Epiclesis: in special invocations the Church calls on God's power and asks that the gifts offered by human hands be consecrated, that is, become Christ's body and blood, and that the victim to be received in communion be the source of salvation for those who will partake.
d) Institutional narrative and consecration: in the words and actions of Christ, that sacrifice is celebrated which He Himself instituted at the Last Supper, when, under the appearance of bread and wine, He offered His body and blood, gave them to His apostles to eat and drink, then commanded that they carry on this mystery.
e) Anamnesis: in fulfillment of the command received from Christ through the apostles, the Church keeps His memorial by recalling especially His passion, resurrection, and ascension.
f) Offering: in this memorial, the Church - and in particular the Church here and now assembled - offers the spotless victim to the Father in the Holy Spirit. The Church's intention is that the faithful not only offer this victim but also learn to offer themselves and so to surrender themselves, through Christ the Mediator, to an ever more complete union with the Father and with each other, so that at last God may be all in all. 
g) Intercessions: the intercessions make it clear that the Eucharist is celebrated in communion with the entire Church of heaven and earth and that the offering is made for the Church and all its members, living and dead, who are called to share in the salvation and redemption purchased by Christ's body and blood.
h) Final doxology: the praise of God is expressed in the doxology, to which the people's acclamation is an assent and a conclusion.
The eucharistic prayer calls for all to listen in silent reverence, but also to take part through the acclamation for which the rite makes provision.
56. Since the eucharistic celebration is the paschal meal, it is right that the faithful who are properly disposed receive the Lord's body and blood as spiritual food as He commanded.  This is the purpose of the breaking of the bread and the other preparatory rites that lead directly to the communion of the people:
a) Lord's Prayer: this is a petition both for daily food, which for Christians means also the eucharist bread, and for the forgiveness of sin, so that what is holy may be given to those who are holy. The priest offers the invitation to pray, but all the faithful say the prayer with him: he alone adds the embolism, Deliver us, which the people conclude with a doxology. The embolism, developing the last petition of the Lord's Prayer, begs on behalf of the entire community of the faithful deliverance from the power of evil. The invitation, the prayer itself, the embolism, and the people's doxology are sung or are recited aloud.
b) Rite of Peace: before they share in the same bread, the faithful implore peace and unity for the Church and for the whole human family and offer some sign of their love for one another.
The form of the sign of peace should take is left to the conference of bishops to determine, in accord with the culture and customs of the people.
c) Breaking of the bread: in apostolic times this gesture of Christ at the last supper gave the entire eucharistic action its name. This rite is not simply functional, but is a sign that in sharing in the one bread of life which is Christ we who are many are made one body (see 1 Cor 10:17).
d) Commingling: the celebrant drops a part of the host into the chalice.
e) Agnus Dei: during the breaking of the bread and the commingling, the Agnus Dei is as a rule sung by the choir or cantor with the congregation responding; otherwise it is recited aloud. This invocation may be repeated as often as is necessary to accompany the breaking of the bread. The final reprise concludes with the words, grant us peace.
f) Personal preparation of the priest: the priest prepares himself by the prayer, said softly, that he may receive Christ's body and blood to good effect. The faithful do the same by silent prayer.
g) The priest then shows the eucharistic bread for communion to the faithful and with them recites the prayer of humility in words from the Gospels.
h) It is most desirable that the faithful receive the Lord's body from hosts consecrated at the same Mass and that, in the instances when it is permitted, they share in the chalice. Then even through the signs communion will stand out more clearly as a sharing in the sacrifice actually being offered. 
i) During the priest's and the faithful's reception of the sacrament the communion song is sung. Its function is to express outwardly the communicants' union in spirit by means of the unity of their voices, to give evidence of joy of heart, and to make the procession to receive Christ's body more fully an act of community. The song begins when the priest takes communion and continues for as long as seems appropriate while the faithful receive Christ's body. But the communion song should be ended in good time whenever there is to be a hymn after communion.
An antiphon from the Graduale Romanum may also be used, with or without the psalm, or an antiphon with psalm from The Simple Gradual or another suitable song approved by the conference of bishops. It is sung by the choir alone or by the choir or cantor with the congregation.
If there is no singing, the communion antiphon in the Missal is recited either by the people, by some of them, or by a reader. Otherwise the priest himself says it after he has received communion and before he gives communion to the faithful.
j) After communion, the priest and people may spend some time in silent prayer. If desired, a hymn, psalm, or other song of praise may be sung by the entire congregation.
k) In the prayer after communion, the priest petitions for the effects of the mystery just celebrated and by their acclamation, Amen, the people make the prayer their own.
d. Concluding Rite
57. The concluding rite consists of:
a) the priest's greeting and blessing, which on certain days and occassions is expanded and expressed in the prayer over the people or another more solemn formulary;
b) the dismissal of the assembly, which sends each member back to doing good works, while praising and blessing the Lord.