Just the facts on religion.


A heresy (Greek, "choice") is a belief or opinion that is contrary to orthodox (accepted and defined) religious doctrine. The term is mainly used in Christianity, Islam, and Judaism.

A person who believes or teaches a heresy is called a heretic; a leader of a heretical teaching or group is known as a heresiarch.

Heterodoxy is a somewhat different term; it usually refers to a teaching that departs from the orthodox but falls short of heresy.