What is the Roman Catholic view on using the term 'orthodox', particularly in regard to Eastern Orthodoxy?

Question

The terms orthodox and catholic have immense significance to those that seek to make exclusive truth claims about their particular Christian Tradition. Both Roman Catholics and Eastern Orthodox trace their descent from (prior to schism) one catholic and orthodox Church. As a result, it would seem to be virtually impossible to concede the exclusive use of one of these terms to "the other side".

How does the Roman Catholic Church view using the terms orthodox or Orthodox generally, but particularly in regard to describing Eastern Orthodoxy?

This is one of a number of related questions I intend to ask regarding the Great (East-West) Schism, terminology and self-identication of the resulting Churches.

The others so far:

• How do the Eastern Orthodox view using the term 'catholic', particularly in regard to Roman Catholicism?
• At what point did the Roman see start self-identifying as the Catholic Church?
• At what point did the Eastern Church start self-identifying as the Orthodox Church?

Answer 1

What is the Roman Catholic view on using the term 'orthodox', particularly in regard to Eastern Orthodoxy?

Anecdotally, "big-O" Orthodox refers to the Eastern or Oriental Orthodox churches, while "little-o" orthodox refers to the literal meaning of "right teaching"

Catholic Encyclopedia says this about the "Orthodox Church" [1]:

The technical name for the body of Christians who use the Byzantine Rite in various languages and are in union with the Patriarch of Constantinople but in schism with the Pope of Rome. The epithet Orthodox (orthodoxos), meaning "right believer", is, naturally, claimed by people of every religion. It is almost exactly a Greek form of the official title of the chief enemies of the Greeks, i.e. the Moslems (mu'min, fidelis). The Monophysite Armenians called themselves ughapar, meaning exactly the same thing. How "Orthodox" became the proper name of the Eastern Church it is difficult to say. It was used at first, long before the schism of Photius, especially in the East, not with any idea of opposition against the West, but rather as the antithesis to the Eastern heretics — Nestorians and Monophysites. Gradually, although of course, both East and West always claimed both names, "Catholic" became the most common name for the original Church in the West, "Orthodox" in the East.

And on "little-o" orthodoxy it says [2]:

Orthodoxy (orthodoxeia) signifies right belief or purity of faith. Right belief is not merely subjective, as resting on personal knowledge and convictions, but is in accordance with the teaching and direction of an absolute extrinsic authority. This authority is the Church founded by Christ, and guided by the Holy Ghost. He, therefore, is orthodox, whose faith coincides with the teachings of the Catholic Church. As divine revelation forms the deposit of faith entrusted to the Church for man's salvation, it also, with the truths clearly deduced from it, forms the object and content of orthodoxy. Although the term orthodox or orthodoxy does not occur in the Scriptures, its meaning is repeatedly insisted on. Thus Christ proclaims the necessity of faith unto salvation (Mark 16:16). St. Paul, emphasizing the same injunction in terms more specific, teaches "one Lord, one faith, one baptism" (Ephesians 4:5, 6). Again, when directing Titus in his ministerial labours, he admonishes him to speak in accord with "sound doctrine" (Titus 2:1). And not only does St. Paul lay stress on the soundness of the doctrine to be preached, but he also directs attention to the form in which it must be delivered: "Hold the form of sound words which thou hast heard of me in faith" (2 Timothy 1:13).

[1] Fortescue, Adrian. "Orthodox Church." The Catholic Encyclopedia. Vol. 11. New York: Robert Appleton Company, 1911. 11 Aug. 2021 http://www.newadvent.org/cathen/11329a.htm.

[2] Callan, Charles. Id. http://www.newadvent.org/cathen/11330a.htm.