Riskiness is a noun: how risky something is — how much chance there is that something bad will happen. You can talk about the riskiness of a plan, a climb, or a loan. It is a slightly stiff, school-book word. In speech people more often say how risky it is, or just the risk. News and school writing still use it when they want to name the quality itself. Though actually, riskiness is not the same as risk. Risk is the chance, or the dangerous thing; riskiness is the “how risky.” A small risk still has some riskiness; a wild idea has a lot.