_Sin is a term used in a religious context to describe an act that violates a moral rule, or the state of having committed such a violation. The moral code of conduct is decreed by a divine entity (such as Yahweh or Allah in the Abrahamic religions).

Sin is often used to mean an action that is prohibited or considered wrong; in some religions (notably some sects of Christianity), sin can refer to a state of mind rather than a specific action. Colloquially, any thought, word, or act considered immoral, shameful, harmful, or alienating might be termed "sinful".