Each Sunday for decades, Roman Catholic priests have offered the blessing - "Lord be with you." And each Sunday, parishioners would respond, "And also with you."

Until this month.

Come Nov. 27, the response will be, "And with your spirit." And so will begin a small revolution in a tradition-rich faith.

At the end of the month, parishes in English-speaking countries will begin to use a new translation of the Roman Missal, the ritual text of prayers and instructions for celebrating Mass. International committees of specialists worked under a Vatican directive to hew close to the Latin, sparking often bitter protests by English speakers over phrasing and readability. After years of revisions negotiated by bishops' conferences and the Holy See, dioceses are preparing anxious clergy and parishioners for the rollout, one of the biggest changes in Catholic worship in generations.

"We're tinkering with a very intimate and personal moment," said the Rev. Richard Hilgartner, executive director of the worship office for the U.S. Conference of Catholic Bishops. "It's public worship, it's the church's official public prayer, but for the individual faithful, it's one of the primary means of their encounter with the Lord."

The biggest challenge will be for priests, who must learn intricate new speaking parts - often late in their years of service to the church.

Many clergy are upset by the new language, calling it awkward and hard to understand.

In the new translation, in the Nicene Creed, the phrase "one in Being with the Father," will change to "consubstantial with the Father." When a priest prays over the Holy Communion bread and wine, he will ask God for blessings "by sending down your spirit upon them like the dewfall."

The new missal grew out of changes in liturgy that started with the Second Vatican Council, the 1960s meetings on modernizing the church that permitted Mass in local languages instead of Latin. Bishops in English-speaking countries created the International Commission on English in the Liturgy to undertake the translation. The panel produced a missal by 1973, but that version was considered temporary until better texts could be completed. As the commission worked to make the Mass more familiar in idiomatic English, some of the language strayed from the Latin. Also in some cases, the commission sought to use language that would be gender neutral.

The work took a new direction in 2001, when the Vatican office in charge of worship issued the directive Liturgiam Authenticam, or Authentic Liturgy, which required translations closer to the Latin. The Vatican also appointed another committee, Vox Clara, or Clear Voice, to oversee the English translation, drawing complaints from some clergy and liturgists that the Vatican was controlling what should be a more consultative process. (Cardinal George Pell, the Sydney, Australia, archbishop and chairman of Vox Clara, has called the complaints baseless and ideologically driven.)