Apostasy (/əˈpɒstəsi/; Greek: ἀποστασία (apostasia), “a defection or revolt”) is the formal disaffiliation from, or abandonment or renunciation of a religion by a person. It can also be defined within the broader context of embracing an opinion contrary to one’s previous beliefs. One who commits apostasy (or who apostatizes) is known as an apostate. The term apostasy is used by sociologists to mean renunciation and criticism of, or opposition to, a person’s former religion, in a technical sense and without pejorative connotation.
Apostasy is generally not a self-definition: very few former believers call themselves apostates because of the negative connotation 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 simply be the voluntary action of its members. Certain churches may in certain circumstances excommunicate the apostate, while some religious scriptures demand the death penalty for apostates. Examples of punishment by death for apostates can be found under the Sharia code of Islam.