Orthodox (lowercase o)
"Correctly believing" — in line with historic Christian teaching, especially the creeds. With a capital O, it means the Eastern Orthodox Church. Same problem as "catholic," one letter over.
What they actually mean
“"Small o: believes the right things. Capital O: the Eastern Orthodox Church. Yes, this is confusing."”
Heard in the wild
“That's a perfectly orthodox position.”
“She converted to Orthodoxy — the Greek church downtown.”
The Lighter Side
Same problem as "catholic," one letter over. Christianity really should have used more words.
The longer version
What it means
Lowercase "orthodox" means right belief — from the Greek orthos (straight, correct) and doxa (opinion, glory). An orthodox Christian holds the faith the church has always held: what the creeds say about God, Christ, the Spirit, salvation, and the resurrection. It's a word of approval ("a thoroughly orthodox theologian") and a boundary ("that view isn't orthodox"). Its opposites: heterodox (other-believing), unorthodox, and, for serious departures, heresy.
Capital-O "Orthodox" is a church: the Eastern Orthodox Church, the second-largest Christian body in the world, with roots in Greece, Russia, the Middle East, and Eastern Europe. It took the name because it claims to have preserved the faith unchanged. So an Orthodox Christian is orthodox, but an orthodox Christian may be Baptist.
Why people say it
Christians use "orthodox" because they need a word for "within the historic faith" that isn't tied to one denomination — a Lutheran and a Catholic can agree that a view is orthodox. The word carries the whole weight of the creeds and councils: this is what Christians have believed. The Eastern church kept it as a name for the same reason, as a claim to continuity.
How to respond
If a Christian calls a view orthodox, they're saying it's within the historic mainstream; if they call it unorthodox, they're flagging a departure, and it's fair to ask what specifically. If someone says they're Orthodox and you're unsure which they mean, "Greek Orthodox?" or "Eastern Orthodox?" will clarify. If a friend converted "to Orthodoxy," they joined the Eastern Orthodox Church — a growing path for some Western Christians drawn to its ancient liturgy. Chesterton's Orthodoxy (1908) is about the lowercase kind.
If you hear it in different churches
Everyone uses the lowercase word; it's the shared vocabulary of Christian theology. Catholics measure orthodoxy by the church's teaching; Protestants by scripture and the creeds; Orthodox by the seven ecumenical councils and the fathers. The Eastern Orthodox Church uses the capital word as its name; Oriental Orthodox churches (Coptic, Armenian, Ethiopian) share the name with a separate history. "Orthodox Jew" is an unrelated use.
Where does “Orthodox (lowercase o)” come from?
The Greek orthodoxos was used by the church fathers from the 300s for those who held the faith of Nicaea against Arians and other heretics. Jude's call to "contend for the faith that was once for all delivered to the saints" is the biblical warrant. After the schism of 1054, the Eastern church styled itself "Orthodox" and the Western church "Catholic," each claiming the descriptive word as a proper name. English kept both lowercase senses alive; "orthodox" as general approval of correct belief has been standard theological English since the 1500s.
Good to know
Lowercase "orthodox" means holding the faith as the creeds define it — the Trinity, Christ's divinity and humanity, the resurrection — and "unorthodox" or "heterodox" means departing from it; "heresy" is the extreme. Any tradition can be orthodox in this sense: an orthodox Baptist, an orthodox Catholic. Capital-O Orthodox is the Eastern Orthodox Church (Greek, Russian, Antiochian, and others), which took the word as its name after the split of 1054. Context and capitalization tell you which; spoken, you may have to ask.
You might also hear
Catholic (lowercase c)
Bible & Theology"Universal" — as in the creeds' "holy catholic church," meaning the whole church of all times and places. Not the same as the Roman Catholic Church.
“"Worldwide, all-of-us. Not Rome, necessarily."”
Sound Doctrine
Bible & TheologyTeaching considered correct, healthy, and faithful to the Bible. "Unsound" is the polite theological word for teaching that isn't.
“"Teaching that's right — and that won't hurt you."”
Icon
Catholic & OrthodoxA sacred painted image of Christ, Mary, or a saint, made in a traditional style and honored — not worshipped — in Orthodox and some Catholic worship.
“"A holy painting that Orthodox Christians kiss, bow to, and pray in front of — as a window, not an idol."”
Go deeper on the network
Common questions
What does "orthodox" mean?+
Lowercase: holding correct, historic Christian belief as the creeds define it. Capital O: the Eastern Orthodox Church.
Is "orthodox" the same as "Orthodox"?+
No, though related. Any Christian can be orthodox (right-believing); only members of the Eastern Orthodox Church are Orthodox. The church took the word as its name.
What's the opposite of orthodox?+
Heterodox or unorthodox (departing from historic belief), and heresy for serious departures.
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Written by Rev. Christopher D.F. Warrington, Ordained Minister, M.Div. · Updated September 2026
This entry was compiled with AI assistance and has not yet been reviewed by an ordained pastor.