A SIN — specifically a sinful ACT, the deed rather than the condition; hamartia is the wider word. ⚠ It carries the crux at Mark 3:29: the earliest text says the blasphemer against the Spirit is guilty of an aiōnion hamartēma, an ETERNAL SIN, and the Byzantine tradition reads aiōniou kriseōs, eternal JUDGEMENT — which is where the KJV's 'in danger of eternal damnation' comes from. The difference is between a condition that does not stop and a penalty that is announced. 'An eternal sin' is a strange expression in Greek as in English, which is the argument for it: a copyist meeting it has an obvious reason to write the familiar word, and no reason runs the other way. ⚠ Mark then supplies his own gloss in the next verse — 'because they were saying, he has an unclean spirit' — which narrows the saying to a specific act: looking at a rescue and calling it demonic. → first discussed at Mark 3:29