What is Sin?
Sin is an act, thought, or condition that violates divine law or moral order. The English word descends from Old English synn. Behind it lie the Hebrew ḥeṭ and the Greek hamartia, both of which carry the literal sense of missing the mark, as an archer misses a target. In the Abrahamic traditions, Judaism, Christianity, and Islam, sin is understood above all as a rupture in the relationship between a person and God. It is named, confessed, and repaired through repentance, atonement, or grace.
Sin vs guilt, evil, and karma
Three nearby ideas get folded into sin and are worth keeping apart. Guilt is the feeling, or the legal status, that follows a wrong; sin is the wrong itself, defined against a divine standard rather than a human court. Evil is a wider category, a name for a force or for the absence of good, while sin is specific and personal, something a person does or becomes. Karma can look similar, since both tie an action to its consequence, but the mechanisms differ. Karma is impersonal and automatic, working through cause and effect. Sin is relational and answerable to a God who can also forgive.
The Abrahamic account
In Judaism sin is ḥeṭ, missing the mark of God's law, and the tradition weighs wrongs against other people heavily, requiring restitution as well as repentance. Its central rite of return is the Day of Atonement, Yom Kippur. Christianity inherited this frame and added the doctrine of original sin, developed most influentially by Augustine of Hippo (354–430) from his reading of the apostle Paul. By that doctrine the whole human race shares in the fault of the first humans and needs redemption through Christ. Islam speaks of dhanb and ithm, deliberate disobedience to God, but rejects inherited sin: each person is born without fault and is accountable only for their own deeds.
Honest disagreement
Original sin is contested within Christianity itself. Augustine's view, that the guilt is inherited, was opposed in his own lifetime by the British monk Pelagius, who held that humans are born morally neutral and sin only by choice. The Eastern Orthodox churches speak instead of ancestral sin: we inherit mortality and a wounded nature, but not personal guilt. Judaism and Islam reject the idea outright. The point here is only that the disagreement is real and old. It is not this entry's place to settle it.
Sin in Indian thought
Hindu and Buddhist traditions have no precise equivalent. The nearest term is pāpa, demerit or wrongdoing, but it works through karma rather than offense against a personal God. Pāpa generates negative karmic residue and binds a person to the cycle of rebirth; it is worn away by merit, ritual, and right action rather than by divine pardon. Buddhism goes further and has no concept of sin as defiance of a deity at all. Harmful acts simply bring consequences through the natural working of cause and effect, though a few grave acts, such as killing a parent or an enlightened being, are held to carry especially heavy weight.
The mystical reading
Inside the contemplative streams of each tradition, sin is often read less as a checklist of forbidden acts than as a single underlying turn: the self curving away from God and toward itself. The mystics tend to locate the trouble in the separate self, the ego that takes itself to be the center of things. On this reading the cure is not mainly moral effort but a reorientation of the whole person, which is what practices like contemplative prayer aim at. The Gnostic currents pushed this furthest, treating ignorance of one's true origin, rather than moral failing, as the deepest fault.
What it isn't
Sin is not simply breaking a rule, and it is not the same as a social taboo, though the words often blur in everyday use. In its religious sense it always implies a standard set by something beyond human convention, and a relationship that the wrong damages. The modern secular use of the word, a sinful dessert or a guilty pleasure, keeps the flavor of transgression while dropping the divine reference that once gave it meaning. This entry describes what the traditions have taught about sin. It makes no claim about what any reader should believe or do.