Ecclesiastical Latin, also called Church Latin or Liturgical Latin, is a form of Latin developed to discuss Christian thought in Late antiquity and used in Christian liturgy, theology, and church administration to the present day, especially in the Catholic Church. It includes words from Vulgar Latin and Classical Latin 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.

Latin is a classical language belonging to the Italic branch of the Indo-European languages. Considered a dead language, Latin was originally spoken in Latium, the lower Tiber area around Rome. Through the expansion of the Roman Republic it became the dominant language in the Italian Peninsula and subsequently throughout the Roman Empire. Even after the fall of Western Rome, Latin remained the common language of international communication, science, scholarship and academia in Europe until well into the early 19th century, when regional vernaculars supplanted it in common academic and political usage—including its own descendants, the Romance languages. For most of the time it was used, it would be considered a dead language in the modern linguistic definition; that is, it lacked native speakers, despite being used extensively and actively.