Foil

Foil may refer to:

Foil (metal), a thin sheet of metal
Aluminium foil
Tin foil
Foil (fencing), a sword without a sharp point
Foil (fluid mechanics), a shape that creates lift when moving
Airfoil, a foil that creates lift in air
Hydrofoil, a foil that creates lift in water
Foil (narrative), a character in a story that contrasts with another character