Deposition, also known as desublimation, is a thermodynamic process, a phase transition in which gas transforms into solid. The reverse of deposition is sublimation. One example of deposition is the process by which, in sub-freezing air, water vapor changes directly to ice without first becoming a liquid. This is how snow forms in clouds, as well as frost and hoar frost on the ground. Another example is when frost forms on a leaf.