Anathema is the most extreme sanction that the Orthodox Church can take against a member of the Church for wrong doing. An anathema is a complete separation, an expulsion, from the Church.
The Orthodox Church distinguishes between excommunication, that is "separation from the communion of the Church", and other penances and anathema. Under excommunication a person remains a member of the Church even though his or her participation in its mystical life, particularly communion, is restricted until the repentance of the one under excommunication. Whereas those under anathema are considered to be completely separated from the Church until repentance.
The two principal causes for which a person may be anathematized are heresy and schism. Anathematization is used by the Church only as a last resort, and must always be preceded by pastoral attempts to reason with the offender to bring about his restoration to the faith.