ST. LOUIS • For the last several weeks, parishioners at St. Margaret of Scotland Catholic Church have been saying goodbye.

The sendoff was not directed at a pastor reassigned to a new church, or a beloved teacher leaving the parish school. Instead, the congregation was bidding farewell to words, and to the comfort of spiritual rituals as familiar to many of them as any practice learned in childhood and cherished ever since.

The most sweeping changes to the Roman Catholic Mass in 40 years are being implemented this weekend for nearly one of every five Catholics around the globe. Nearly 200 million believers across all 11 of the church's English-speaking conferences — the United States, Australia, Canada, England and Wales, India, Ireland, New Zealand, Pakistan, the Philippines, Scotland, and South Africa — are changing to the new English-language translation of the prayers, chants and responses used in the Catholic Mass.

Bishops, priests and deacons in the St. Louis archdiocese and the Belleville diocese have been educating themselves and the laity for nearly two years about the new translation, which moves the liturgy closer to the original Latin.

Bishops chose to introduce the new text, called the Roman Missal, Sunday because it's the beginning of Advent, the four-week season of anticipation leading up to Christmas, and the start of a new liturgical year in the church.

With the largest parish in the St. Louis Archdiocese, Monsignor James Callahan, pastor of St. Joseph in Cottleville, has a lot of people to catechize — 5,068 households' worth.

"At first, most Catholics were saying, 'Why are we doing this? It's not like the Mass was broken,'" Callahan said. "So we explained in more detail why these changes were happening by going back to the Latin text and showing that this is a more literal translation, including richer biblical references and more theologically accurate expressions."

For the last seven weeks, pastoral leaders at St. Margaret of Scotland, in the city's Shaw neighborhood, have ushered parishioners through a "Festival of Glorias," seven musical settings of the Gloria, a well-loved prayer typically sung during the Mass, which will be slightly longer and more formal in the new translation.

The parish also said goodbye to one of four portions of the Eucharistic prayer called "memorial acclamations." The new translation of the missal dictates that everything said in the Mass has to be a translation of the original Latin text. But in the years after the Second Vatican Council, when the most recent text was developed, the now-familiar memorial acclamation, "Christ has died, Christ is risen, Christ will come again," somehow found its way into the English-language liturgy. Since there was never a Latin version of the acclamation, it has disappeared from the Mass forever.

"Missals" are simply books of prayers, first found in 12th-century monasteries. According to the U.S. Conference of Catholic Bishops, the first Missale Romanum appeared in 1474, soon after the advent of the printing press. A century later, after the Council of Trent, Pope Pius V mandated the use of the Roman Missal, the first attempt to coordinate the celebration of Mass throughout the church. From 1602 to 1975, five popes updated the liturgy by implementing new versions of the missal.

Catholics celebrated Mass in Latin in the United States until 1964, and in 1973 English-speaking bishops around the world officially implemented the changes to the liturgical text set down by the Second Vatican Council in the mid-1960s. By translating the missal from Latin into each country's vernacular, bishops at the council believed Catholics would get more out of the Mass.

But almost immediately there were complaints about the accuracy and spirit of the translations. The Vatican issued a revised text in 1975, but Pope John Paul II did not think those revisions went far enough, so in 2002 he introduced the new translations to encourage greater fidelity to the original Latin.

After years of debate, the bishops finally approved the English translation in 2006 and the Vatican confirmed it in 2008.

In November 2010, the St. Louis Archdiocese kicked off its missal education campaign with a two-day workshop open to anyone. While the laity will have to learn about a dozen new phrases within familiar prayers, the challenge for pastors is much larger. Changes to everything from essential portions of the Mass to short, seasonal prayers number in the thousands for priests, some of whom have begun joking that their noses will be so buried in the new books that their parishioners will eventually cease to recognize them.

This spring, St. Louis Archbishop Robert Carlson's office sent audio recordings of the most common Eucharistic prayers to priests and deacons so they could hear the new wording. In the summer, priests and deacons received study texts, and members of the International Commission on English in the Liturgy — the central body involved in the translation — came to St. Louis and Belleville to speak to priests and answer questions. The archdiocese's sacred music office held three workshops for parish musicians and pastors.

The archdiocese sent 30,000 copies of an informational booklet called "Understanding the Revised Roman Text," to parishes, along with 45,000 pew cards — essentially cheat sheets — for people to use as they get used to the new wording.

Catholics were not allowed to use the new missal until this weekend, so — aside from some music — practice could not happen during Mass. Sue Huett, director of the Belleville diocese's worship office, said in recent months pastors regularly held short sessions so their congregations could practice before and after Mass.

Sister Catherine Vincie, a professor of liturgical theology at the Aquinas Institute of Theology in St. Louis, said there's been "a good amount" of preparation by church leaders. "In those pockets where there's been substantial work done it's not going to come as a shock," she said. "But in some parishes, there hasn't been so much preparation, and I think people are going be surprised by what's coming."

One major change comes in the Nicene Creed, the ancient profession of Christian faith that Catholics recite together during the Mass. Until today, English-speaking Catholics expressed the theology of the Trinity in the creed by saying Jesus was "one Being with the Father." The new translation says Jesus was "consubstantial with the Father." Consubstantial is a more precise reflection of the original Latin, but it's also a word that most Catholics are unfamiliar with, and promises to trip them up, at least for a while.

Bishops and priests largely view the prospect of reteaching Catholics the meaning of the words they say in church each Sunday as a gift. Despite the stumbles and confusion certain to occur in the pews and from the altar in the next several months, this is a chance for the church to seize an opportunity for deeper theological reflection, they say.

None of the changes, including the word "consubstantial" in the Nicene Creed, is meant to trip people up, said Monsignor William McCumber, director of the archdiocese's worship office.

"It's about whether Christ is of a like substance, or the same substance, as the Father," he said. "There's a tremendous history in the church behind that word, and this is a chance to teach people about it. The underlying principal of these changes is about what we believe as a church, reflected in the words we say in church.

"Lex orandi, lex credendi," McCumber added. "The rule of prayer is the rule of faith."

EDITOR'S NOTE: The date of when English-speaking churches began using English in the liturgy has been corrected in this story.