Answer: Frost
Explanation: Frost is the deposition of ice, that develops after the freezing of the water vapor. It most commonly appears on the surfaces of the ground and can be observed as fragile crystals of ice. These can be observed on the window panes, blades of the grass, or any other solid exposed surface. The window frost develops when a pane of glass is exposed to below freezing temperature from the outer surrounding and the moist air from inside.