Not To Be Confused With
Orthodoxy is right BELIEF; orthopraxy is right PRACTICE. (Capital-O “Orthodox” also names the Eastern Orthodox communion — a different use of the word.)
Orthodoxy comes from Greek orthos (“right, straight”) + doxa (“opinion,” and also “glory/worship”) — so it means both right belief and right worship. In practice it names the core Christian faith confessed by the whole Church: the Trinity, the full deity and humanity of Christ, the resurrection, salvation by grace — the things defined at Nicaea, Constantinople, Ephesus, and Chalcedon.
Theologos uses “orthodoxy” for the shared Nicene faith that Orthodox, Catholic, and Protestant Christians hold in common — not for any one tradition's distinctives. Disagreements inside that shared faith are intramural, not a breach of orthodoxy.