Frost is the thin layer of ice crystals that forms on surfaces when water vapor in the air freezes. On cold mornings, you might see frost covering car windshields, grass blades, and window panes, creating delicate white patterns that look like feathers or ferns. When the temperature drops below freezing (32°F or 0°C), moisture in the air skips the liquid stage and transforms directly into ice, coating everything it touches.

Frost can be beautiful: Jack Frost, the legendary winter sprite of folklore, supposedly paints those intricate patterns on windows during cold nights. But frost can also be destructive. Farmers worry about late spring frosts that can kill young plants and ruin crops. Gardeners cover delicate plants with sheets or blankets when frost is forecast to protect them from freezing.

The word also means to cover something with a thin coating, like when you frost a cake with icing. You might frost cupcakes for a birthday party, spreading a sweet layer across the top. Some people even frost their hair, adding light-colored highlights that look a bit like frost on dark soil.