In religious context, sin is a transgression against divine law or a law of the deities. Each culture has its own interpretation of what it means to commit a sin. While sins are generally considered actions, any thought, word, or act considered immoral, selfish, shameful, harmful, or alienating might be termed "sinful".

The concept of sin originates from the Old English synn, tracing back to Proto-Germanic and Proto-Indo-European roots meaning “being” or “truly guilty,” implying a judgment of wrongdoing. Over time, different religions and cultures developed distinct understandings of sin, often shaping moral frameworks and spiritual practices.

In Buddhism, sin as defiance against a deity does not exist; instead, actions naturally bring consequences through karma. While general “sin” refers to transgressions against universal moral law, five acts — harming a Buddha, killing an Arhat, creating schism in the Sangha, matricide, and patricide — are considered so severe that they bring immediate karmic repercussions. In contrast, Shinto views sin (tsumi) as impurity caused by external factors like evil spirits, not inherently by human actions, and emphasizes purification rituals (harae) to restore harmony.

In Abrahamic religions, sin carries a stronger theological dimension. Christianity treats sin as an offense against God, rooted in disobedience, with doctrines like original sin and redemption through Christ’s sacrifice; concepts like the seven deadly sins classify vices leading to moral corruption. Islam defines sin (khiṭʾ, ithm) as violating God’s commands, distinguishing between minor and grave sins. Judaism frames sin as “missing the mark” of God’s law, placing greater weight on wrongs against other people than against God, with atonement often requiring repentance and restitution.

From Middle English sinne, synne, sunne, zen, from Old English synn ("sin"), from Proto-West Germanic *sunnju, from Proto-Germanic *sunjō ('truth', 'excuse') and *sundī, *sundijō ("sin"), from Proto-Indo-European *h₁s-ónt-ih₂, from *h₁sónts ("being, true", implying a verdict of "truly guilty" against an accusation or charge), from *h₁es- ("to be"); compare Old English sōþ ("true"; see sooth). Doublet of suttee.

There are a few differing Buddhist views on sin. American Zen author Brad Warner states that in Buddhism there is no concept of sin at all. The Buddha Dharma Education Association also expressly states "The idea of sin or original sin has no place in Buddhism."

Ethnologist Christoph von Fürer-Haimendorf explained, "In Buddhist thinking the whole universe, men as well as gods, are subject to a reign of law. Every action, good or bad, has an inevitable and automatic effect in a long chain of causes, an effect that is independent of the will of any deity. Even though this may leave no room for the concept of 'sin' in the sense of an act of defiance against the authority of a personal god, Buddhists speak of 'sin' when referring to transgressions against the universal moral code."

However, there are five heinous crimes in Buddhism that bring immediate disaster through karmic process. These five crimes are collectively referred to as Anantarika-karma in Theravada Buddhism and pañcānantarya (Pāli) in the Mahayana Sutra Preached by the Buddha on the Total Extinction of the Dharma, The five crimes or sins are: