Heresy refers to beliefs or opinions that deviate from established doctrines, particularly in a religious context. It often involves rejecting or altering core tenets of faith, which can lead to conflict within a religious community. Historically, heresy has been met with severe consequences, including excommunication or persecution. The term is most commonly associated with Christianity, where early church leaders sought to define orthodoxy. Notable examples of heretical movements include Arianism, which questioned the nature of Jesus Christ, and Gnosticism, which offered alternative interpretations of spiritual knowledge.