Apostasy in Christianity is the repudiation of Christ and the central teachings of Christianity by someone who formerly was a Christian (Christ-follower). The term apostasy comes from the Greek word apostasia ("ἀποστασία") meaning "rebellion", "state of apostasy", "abandonment", or "defection". 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."
B. J. Oropeza, who has written one of the most exhaustive studies on the phenomenon of apostasy in the New Testament (3 Volumes, 793 pages), "uncovered several factors that result in apostasy." Some of these factors overlap, and some Christian communities were "susceptible to more than one of these." The first major factor in a believer committing apostasy (i.e., becoming an unbeliever) is "unbelief." Other factors potentially leading to apostasy include: "persecution," "general suffering and hardship," "false teachings and factions," "malaise," "indifference and negligence towards the things of God" (specifically, "the command to love one's neighbors"), and engaging in sinful acts ("vice-doing") or assimilating to the ungodly attitudes and actions reflected in a non-Christian culture.
For additional biblical teaching on the possibility of apostasy see
The Greek noun apostasia (rebellion, abandonment, state of apostasy, defection) is found only twice in the New Testament (Acts ; 2 Thessalonians ). However, "the concept of apostasy is found throughout Scripture." The related verb aphistēmi (go away, withdraw, depart, fall away) carries considerable theological significance in three passages (Luke 8:13; 1 Timothy 4:1; Hebrews 3:12).