A coating is a layer of material that covers the surface of something else. When you dip a pretzel in chocolate, the chocolate forms a smooth coating around it. When painters apply a coating of paint to a wall, they're protecting and changing the surface underneath.

Coatings serve different purposes depending on what they're made of and what they're covering. A thin coating of wax protects your car's paint from weather and dirt. A coating of varnish makes wooden furniture shine while protecting it from scratches. Pills often have a coating that makes them easier to swallow and helps them dissolve at the right time in your body. Even your tongue can have a coating on it (which is why you might brush it when you brush your teeth).

The thickness and type of coating matter. A light dusting of powdered sugar is a thin coating on a donut, while the rubber coating on electrical wires is thick enough to prevent dangerous shocks. Scientists and engineers design special coatings for all kinds of purposes: non-stick coatings for pans, waterproof coatings for jackets, and even special coatings for spacecraft that can withstand incredible heat.