Apostasy is generally not a self-definition: very few former believers call themselves apostates because of the pejorative implications of the term. Many religious groups and some states punish apostates. Apostates may be shunned by the members of their former religious group or subjected to formal or informal punishment. This may be the official policy of the religious group or may be the action of its members. Certain churches may in certain circumstances excommunicate the apostate, while some religious scriptures demand the death penalty for apostates. Apostasy in Christianity refers to the rejection of Christianity by someone who formerly was a Christian.
The term apostasy comes from the Greek word apostasia meaning defection, departure, revolt or rebellion. It has been described as "a willful falling away from, or rebellion against, Christianity. Apostasy is the rejection of Christ by one who has been a Christian...." "Apostasy is a theological category describing those who have voluntarily and consciously abandoned their faith in the God of the covenant, who manifests himself most completely in Jesus Christ. "Apostasy is the antonym of conversion; it is deconversion."