When a substance has a triple point above 1 atm (atmospheric pressure), it can be said to sublime at 1 atm. The triple point can be defined as one point where a substance's solid, liquid, and vapor form come together in a three-point equilibrium. Subliming can be defined as the transformation of a substance from a solid directly to a vapor, bypassing a liquid form. This is because the liquid form only exists when the atm is higher than its triple point for this particular substance.
