Translators wanted the Mass to sound more like the original Latin.
Critics say the revision's stilted language and occasional 88-word run-on sentence will turn off parishioners.
Church leaders acknowledge the transition will require adjustment and explanation, but they insist members will grow comfortable with the new language in time.
"After we've been doing this six months, people are going to wonder, 'What did we used to say?' " said the Rev. Joshua Brommer, liturgical coordinator for the Diocese of Harrisburg. "For the Catholic who comes to Mass each Sunday, it will not take long for these words to become part of their prayer life."
The changes take effect the first Sunday of Advent (Nov. 27), the start of the liturgical year. Churches will use a new English translation of the Mass that's being introduced across the English-speaking world this year. Catholics in South Africa and Australia are already worshipping with it.
The current text dates to 1973 when haste in translation led to the revisions. Church authorities say the new version is more theologically accurate and closer to the original Latin.
The Vatican has been pushing this change for more than a decade: It wants the English liturgies to mimic the words and even the syntax of the original Latin prayers.
Brommer hopes the process of learning the revised Mass will inspire Catholics to consider anew its meaning.
"These words might feel a little foreign to us at times, and certainly not words we hear in everyday conversation, but the celebration of Mass is not an everyday experience," he said.
Some aren't convinced of the new missal's benefits and have launched campaigns to stop it.
More than 22,000 priests, nuns and lay people from more than 60 countries have signed an online protest, "What If We Just Said Wait," led by a Seattle priest hoping to postpone implementation of the text.
