: ''This article deals with orthodoxy (lowercase o), a general term for right religious belief or practice. For more information about the Orthodox Church, see [[Introduction to Orthodox Christianity]]. ''
The word '''''orthodoxy''''', from the [[Greek language|Greek]] ''
orthos'' (' straight', 'correct') and ''doxa'' ('thought', 'teaching', ' glory'), is used to refer to the correct [[ theology|theological]] or [[ doctrine|doctrinal]] observance of religion, as determined by some overseeing body. The term did not conventionally exist with any degree of formality (in the sense in which it is now used) prior to the advent of Christianity in the Greek-speaking world, though the word does occasionally show up in ancient literature in other, somewhat similar contexts. Orthodoxy is opposed to ''[[heterodoxy]]'' ('other teaching'), ''[[heresy]]'' and ''[[schism]]''. People who deviate from orthodoxy by professing a doctrine considered to be false are most often called heretics, while those who deviate from orthodoxy by removing themselves from the perceived body of believers, i.e. from [[full communion]], are called schismatics. Not infrequently these occur together. The distinction in terminology pertains to the subject matter; if one is addressing corporate unity, the emphasis may be on schism; if one is addressing doctrinal coherence, the emphasis may be on heresy.
Derived from late classical and [[medieval]] Christian apologetics for orthodoxy, more specifity is often applied when defending a claim to orthodoxy or refuting heresy. ''[[Apostasy]]'', for example is a violation of orthodoxy that takes the form of abandonment of the [[faith]], be it for some form of [[atheism]] or for some other faith, a concept largely unknown before the adoption of Christianity as the official religion of Rome. The first well-known apostate is probably [[Julian the Apostate|Julian]], the last [[paganism|pagan]] emperor of Rome. A lighter deviation from orthodoxy than heresy is commonly called ''error'', in the sense of not being grave enough to cause total estrangement while yet seriously affecting communion. Sometimes ''error'' is also used to cover both full heresies and minor errors.
In English, the term "[[Oriental Orthodoxy]]" is used to refer to non-Chalcedonian eastern Christians, as opposed to Christians of Eastern Orthodox Churches, who accept the [[Council of Chalcedon]] (See [[Ecumenical Councils]])and generally worship according to the Byzantine Rite. They are found in Egypt, Ethiopia, some parts of Syria, Iraq and Iran, Armenia,and southern India in Kerala State.They accept only the first three of the Oecumenical councils. In the last century there has been some rapproachement between these and the Eastern Orthodox Churches, particularly in Syria. There have been claims after dialogue, that really the differences have been of phraseology all along, and a simple misunderstanding of what each church holds. This is not entirely satisifactory to many Eastern Orthodox,and it is not considered in each church's competence to use a General Holy Synod to bring about communion. These Eastern Orthodox Christian hold that it would take another Great and Holy Council of every Eastern Orthodox Bishop together to reverse the Anathema, and this raises problems of its own.