Mortal sin

In Catholic moral theology, a mortal sin is a grave offense committed with full knowledge and deliberate consent. It destroys charity in the sinner and separates them from God.

Grave matter: A serious violation of divine or moral law, such as murder or adultery. Mortal sin requires an offense involving grave matter.
Sin: An act or disposition understood as a freely chosen offense against God and moral order. Mortal sin is a particular kind of sin defined by grave matter and full consent.
First Letter of John: A New Testament letter that contrasts sin leading to death with sin not leading to death. Its distinction became a key scriptural basis for mortal and lesser sin.
Original sin: The inherited condition of humanity's estrangement from God, distinguished from personal acts of sin. It contrasts an inherited condition with a personally chosen grave offense.
Full knowledge: Awareness that an act is seriously wrong when it is chosen. Ignorance can diminish or remove responsibility for grave wrongdoing.
Confession (sacrament): The Catholic sacrament in which sins are confessed to a priest and absolution is given. It is the ordinary sacramental means of reconciliation after mortal sin.
Augustine of Hippo: A late antique Christian theologian whose writings shaped Western accounts of sin, grace, and the will. His theology of sin and grace influenced later Latin Christian teaching.
Once saved, always saved: The belief that a person truly saved by God cannot ultimately lose salvation. It contrasts with accounts in which grave sin can rupture communion with God.
Deliberate consent: A free and intentional choice to perform an act despite knowing its moral character. Mortal sin requires consent that is sufficiently deliberate.
Absolution: The remission of sins pronounced by a priest in the sacrament of penance. Absolution restores the sinner's communion with God when the sacrament is received worthily.

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