Foil is a very thin, flat sheet of metal. People use it in the kitchen to cover food and keep it fresh or hot.
We use foil to cover the food.
The foil keeps the heat inside.
To foil something means to stop it from working or happening. It often means stopping bad plans or tricks.
The police foil the bad plan quickly.
He tried to cheat, but we foiled him.
In stories, a foil is a character who is very different from another. This difference helps show the other character’s strengths or weaknesses.
His calmness is a foil to her anger.
The hero’s friend is a foil in the story.
To foil can mean to shine or sparkle by reflecting light. This is often used for shiny surfaces or materials.
The moonlight foils on the water.
Her silver dress foils in the light.
In electronics, foil is a thin metal layer used around wires or parts. It blocks unwanted electrical signals and protects devices.
The wire has a copper foil shield.
Foil protects the signal well.
