Latin

Latin has remained the Roman Catholic Church's official language for canon law, major papal documents, and the church's internal governance for close to two thousand years, even as the everyday language of ordinary Catholic worship shifted decisively toward local vernaculars following the Second Vatican Council's reforms in the 1960s.

The Codex Iuris Canonici, the Catholic Church's body of canon law, is authoritatively promulgated in Latin, with vernacular translations treated as aids to understanding rather than the binding legal text itself, a practice that keeps Latin functionally central to Catholic institutional life even where it is rarely spoken. Major papal documents, including encyclicals, are still customarily issued with an official Latin text alongside vernacular translations, and the Vatican maintains a Latin language office responsible for rendering modern administrative and theological concepts, including contemporary technology and institutions, into classical Latin vocabulary.

The Tridentine Mass, celebrated entirely in Latin, was the standard form of the Roman Catholic liturgy for roughly four centuries following the Council of Trent in the sixteenth century, and it continues to be celebrated today by some communities under permissions the church has granted for its continued limited use alongside the modern vernacular liturgy. Latin's continued institutional role gives the Catholic Church a documentary continuity across language shifts elsewhere in its history that few other global religious institutions can match, since a scholar today can read a papal document from centuries ago in essentially the same official language used for one issued this year.

Jerome's Latin translation of the Bible, known as the Vulgate and completed in stages around the turn of the fifth century, became the standard biblical text of Western Christianity for over a thousand years, shaping Catholic theological vocabulary so thoroughly that many core Latin theological terms passed largely unchanged into English and other European languages through it.

The Council of Trent in the sixteenth century formally declared the Vulgate authoritative for Catholic doctrine and liturgy, cementing a status it had already held informally for centuries, and Catholic biblical scholarship continued to reference and revise the Vulgate text, including a major twentieth century revision, well after other confessions had shifted toward translations from the original Hebrew and Greek. Latin was also the working language of Western scholastic theology, the systematic method of argument, definition, and disputation developed in medieval universities and applied most influentially by Thomas Aquinas in works including the Summa Theologica, which addressed questions ranging from the nature of God to the ethics of everyday conduct using a rigorous Latin technical vocabulary largely built for the purpose. This shared Latin scholarly language let theologians across different countries engage directly with each other's arguments without translation, producing a genuinely international medieval intellectual culture organized around Latin universities. Scholastic Latin terminology, including concepts such as substance, accident, and the several senses distinguished for scriptural interpretation, remains part of the working vocabulary of Catholic theology today, even in discussions conducted primarily in modern languages.