Apostasy (from Greek ?????????, meaning a defection or revolt, from ???, apo, "away, apart", ??????, stasis, "standing") is a term generally employed to describe the formal abandonment or renunciation of one's religion, especially if the motive is deemed unworthy. In a technical sense, as used sometimes by sociologists without the pejorative connotations of the word, the term refers to renunciation and criticism of, or opposition to one's former religion. One who commits apostasy is an apostate, or one who apostatises. Apostasy is generally not a self-definition: very few former believers call themselves apostates and they generally consider this term to be a pejorative. One of the possible reasons for this renunciation is loss of faith, another is the failure of alleged religious indoctrination or brainwashing.Many religious movements consider it a vice (sin), a corruption of the virtue of piety in the sense that when piety fails, apostasy is the result.Many religious groups and eve
Source:
http://en.wikipedia.org/wiki/Apostasy