Ruthenian Greek Catholic Church in the context of "Use (liturgy)"

Ruthenian and Ruthene are exonyms of Latin origin, formerly used in Eastern and Central Europe as common ethnonyms for East Slavs, particularly during the late medieval and early modern periods. The Latin term Rutheni was used in medieval sources to describe all Eastern Slavs of the Grand Duchy of Lithuania, as an exonym for people of the former Rus', thus including ancestors of the modern Belarusians, Rusyns and Ukrainians. The use of Ruthenian and related exonyms continued through the early modern period, developing several distinctive meanings, both in terms of their regional scopes and additional religious connotations (such as affiliation with the Ruthenian Greek Catholic Church).

In medieval sources, the Latin term Rutheni was commonly applied to East Slavs in general, thus encompassing all endonyms and their various forms (Belarusian: русіны, romanized: rusiny; Ukrainian: русини, romanized: rusyny). By opting for the use of exonymic terms, authors who wrote in Latin were relieved from the need to be specific in their applications of those terms, and the same quality of Ruthenian exonyms is often recognized in modern, mainly Western authors, particularly those who prefer to use exonyms (foreign in origin) over endonyms.