A transgression is a crossing of a boundary that should not have been crossed. In religious language the boundary is set by divine command; the act is therefore not merely a mistake but a violation of a relationship.

Biblical Hebrew uses several words for the idea—sin, iniquity, rebellion—each with its own shade. Transgression often carries the sense of deliberate overstepping. The first humans eat the forbidden fruit; Israel breaks the covenant; the individual chooses what God has forbidden. The consequence is disruption: between the person and God, between the person and others, and within the person. Guilt, shame, and the need for restoration follow.

In Christian theology every transgression is ultimately against God, even when the immediate harm is horizontal. The law makes the boundary clear; conscience and the Spirit confirm it. Forgiveness is possible, yet it is not automatic. Confession and repentance are the appointed path back across the boundary in the right direction.

The word still works outside explicitly religious settings. To call an act a transgression is to claim that some lines matter and that crossing them damages more than the rules themselves.