Answer:
Heresy in Christianity denotes the formal denial or doubt of a core doctrine of the Christian faith[1] as defined by one or more of the Christian churches.[2]
In Western Christianity, heresy most commonly refers to those beliefs which were declared to be anathema by any of the ecumenical councils recognized by the Catholic Church.[citation needed] In the East, the term "heresy" is eclectic and can refer to anything at variance with Church tradition. Since the Great Schism and the Protestant Reformation, various Christian churches have also used the concept in proceedings against individuals and groups deemed to be heretical by those churches.
The study of heresy requires an understanding of the development of orthodoxy and the role of creeds in the definition of orthodox beliefs, since heresy is always defined in relation to orthodoxy. Orthodoxy has been in the process of self-definition for centuries, defining itself in terms of its faith, and changing or clarifying beliefs in opposition to people or doctrines that are perceived as incorrect.
