The chance of harm, weighed against its size. Risk is respected rather than feared — the two produce opposite decisions.
Italian risco / rischio (danger, hazard), of disputed origin — one line traces it to Latin resecare (to cut off short), by way of the hazard a ship's course runs against a jagged coast; entered English through French risque.
The chance of harm, sized against what it would cost — a thing to be weighed and respected rather than feared, since the two produce opposite decisions.