Various groups have laid claim to the word ''orthodox'' as part of their titles, usually in order to differentiate themselves from other, 'heretical' movements. [[Orthodox Judaism]] focuses on a strict adherence to what it sees as the correct interpretation of the [[Oral Torah]], dating from the revelation of the Torah on [[Mount Sinai]]. Within Christianity, the term occurs in the [[Eastern Orthodoxy|Eastern Orthodox]], [[Western Orthodoxy|Western Orthodox]], and [[Oriental Orthodoxy|Oriental Orthodox]] churches as well as in [[Protestantism|Protestant]] [[religious denomination|denomination]]s like the [[Orthodox Presbyterian Church]].
The Eastern Orthodox Churches hearken back to the original forms of worship; for example, the [[Nicene Creed]] is used as created at the [[First Council of Constantinople]] in 381, in contrast to the [[Roman Catholic]] church, which use the Nicene creed with the addition of the phrase 'and the Son' (see [[Filioque
clause]]). This change is one of many causes for the Great Schism formalized in 1054 by simultaneous proclamations of [[Anathema#Anathema_in_the_Catholic_Church|"Anathema"]] from the collegial leadership of the Orthodox Churches in the East and the Bishop of Rome in the West. This emphasis on the use of the original "creed" is shared today by all Eastern Orthodox churches.
The Catholic Church considers the Eastern Orthodox to be in schism and therefore not in [[full communion]] with the [[Holy See]]. Some of Eastern Orthodox Christians in turn consider Roman Catholics to be heretics, while the majority consider them in schism.