A = Abbot or Abbess (the "father" or "mother" superior of a monastery).
Ap= Apostle (one of the 12 appointed by Christ; St. Matthias, St. Paul, or St. Barnabas).
B = Bishop (one given the fullness of the priesthood by the apostles or their successors).
BVM= The Blessed Virgin Mary, mother of Jesus Christ, true God, and true man.
C = Confessor (a holy man; priest, religious, or lay).
DC= Doctor of the Church (one designated by the Church as a scholar of the highest repute).
Ev= Evangelist (one of the writers of the four Gospels).
K = King (often simply designated "C" for confessor.
M = Martyr (one whose life was taken for professing the true Faith).
P = Pope (the Bishop of Rome, Successor of Saint Peter, and Vicar of Christ on Earth).
V = Virgin (a woman dedicated to Christ, to the exclusion of all others.
W = Widow (a holy woman; religious or lay).
Abbreviations may be doubled to indicate plurality (e.g. "MM" or "PP" or "CC" might be used to refer to two or more martyrs, or two or more popes, or two or more confessors). Abbreviations may be concatenated. "P.DC." refers to a Pope who was also a doctor of the church
On certain days of the year, a "stational church" may be noted, (designated "STN") although this is done solely for historical interest. In years past, the Pope and the people of Rome went in procession and gathered at the stational church to celebrate the days feast. All of these churches are located at Rome -- even one named the "Holy Cross in Jerusalem" -- but a few of them are located "outside the walls."
The ordo lists the changeable prayers that will be recited or sung by the priest on the Sundays and Feast days of the month. It is an abbreviated version of the ordo that might be employed in a diocese or religious order, giving directions for finding the changeable prayers of the Mass and Divine Office in the Missal and Breviary.
The Ordo will include: The vestment color of the day; white, red, green, purple, rose, or black. Cloth of gold may be substituted for white, red, or green. Cloth of silver may be used in place of white. Purple may be substituted for rose. In Florida, because of its Spanish origins, light blue may be used on the feast of the Immaculate Conception of our Lady and on other major Marian feasts.
The rank of the feast; first, second, or third. Important feasts may be celebrated with an "octave," meaning that they are celebrated liturgically for eight days. Feasts with "privileged" octaves are celebrated, or, at least commemorated during each of the eight days. Those with a "common" octave yield to feasts of the same person or to greater feasts. A "simple" octave is celebrated or commemorated only on the first and eighth days. Of the "privileged" octaves, Easter and Pentecost have a proper Mass and Office for each day; Epiphany and Corpus Christi exclude all feasts below the second class within their octaves; Christmas and the Ascension must always be commemorated during their octaves.
Advice as to whether the Gloria and/or Creed are to be said, as well as to which preface is required. Some special feasts and octaves have a proper Communicantes and Hanc igitur within the Canon. If the dismissal is something other than "Ite, missa est," this will be noted. Under certain circumstances, some Masses have a Last Gospel other than the first fourteen verses of St. John.
The prayers to be added to the Collect, Secret, and Postcommunion of the day, are referred to as second (and third) prayers or orations. The traditional order is presented, while acknowledging that Pope Pius XII granted great latitude to priests and bishops in determining the subject and number of such prayers.
The calendar and consequently the Ordo may vary slightly from diocese to diocese. Some feasts are celebrated in one country and not in another, or they may be celebrated with varying degrees of rank. Most nations have a national patron. The day of the dedication of a church and the feast day of its patron are observed with higher rank in that church. The churches of religious orders may observe a considerably different schedule of feasts than their counterparts in the churches of the diocese.
Likewise, the days for fasting and abstinence may vary somewhat with local custom and the observance of local feasts. The Ember Days of Fall are traditionally the Wednesday, Friday, and Saturday following the Exaltation of the Holy Cross (September 14), but some churches follow a newer calendar in which these days are fixed on the Wednesday, Friday, and Saturday of the third full week in September -- causing an occasional discrepancy.