Ecclesiastical Latin, also called Church Latin, Liturgical Latin or Italian Latin, is a form of Latin initially developed to discuss Christian thought and later used as a lingua franca by the Medieval and Early Modern upper class of Europe. It includes words from Vulgar Latin and Classical Latin (as well as Greek and Hebrew) re-purposed with Christian meaning. It is less stylized and rigid in form than Classical Latin, sharing vocabulary, forms, and syntax, while at the same time incorporating informal elements which had always been with the language but which were excluded by the literary authors of classical Latin.
Its pronunciation was partly standardized in the late 8th century during the Carolingian Renaissance as part of Charlemagne's educational reforms, and this new letter-by-letter pronunciation, used in France and England, was adopted in Iberia and Italy a couple centuries afterwards. As time passed, pronunciation diverged depending on the local vernacular language, giving rise to even highly divergent forms such as the traditional English pronunciation of Latin, which has now been largely abandoned for reading Latin texts. Within the Roman Catholic Church and in certain Protestant churches, such as the Anglican Church, a pronunciation based on modern Italian phonology became common during the 20th century.
Ecclesiastical Latin was the language of liturgical rites in the Catholic Church, as well as the Anglican Church, Lutheran Church, Methodist Church, and in the Western Rite of the Eastern Orthodox Church. Today, ecclesiastical Latin is primarily used in official documents of the Roman Catholic Church, in the Tridentine Mass, and it is still learned by clergy.
The Ecclesiastical Latin that is used in theological works, liturgical rites and dogmatic proclamations varies in style: syntactically simple in the Vulgate Bible, hieratic (very restrained) in the Roman Canon of the Mass, terse and technical in Thomas Aquinas's Summa Theologica, and Ciceronian (syntactically complex) in Pope John Paul II's encyclical letter Fides et Ratio.