Foil

A foil is a type of practice weapon used in fencing. See foil (sword)

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Foil can also refer to a hydrofoil, a type of boat.

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A related yet different meaning of foil is airfoil, a type of wing or blade.

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Foil can also be a short form of the longer noun aluminium foil, a type of wrapping for food, as in "I've wrapped the sandwiches in foil".

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A foil is also a type of character in literature. See foil (literature)