Foil may refer to:

Materials

Foil (metal) A foil is a very thin sheet of metal, typically made by hammering or rolling. Foils are most easily made with malleable metal, such as aluminium, copper, tin, and gold. Foils usually bend under their own weight and can be torn easily. For examp ...

, a quite thin sheet of metal, usually manufactured with a rolling mill machine *

Metal leaf A metal leaf, also called composition leaf or schlagmetal, is a thin foil used for gilding and other forms of decoration. Metal leaves can come in many different shades, due to the composition of the metal within the metal leaf. Examples of this ...

, a very thin sheet of decorative metal *

Aluminium foil Aluminium foil (or aluminum foil in American English; occasionally called tin foil) is aluminium prepared in thin metal leaves. The foil is pliable and can be readily bent or wrapped around objects. Thin foils are fragile and are sometimes ...

, a type of wrapping for food *

Tin foil Tin foil, also spelled tinfoil, is a thin foil made of tin. Tin foil was superseded after World War II by cheaper and more durable aluminium foil, which is still referred to as "tin foil" in many regions (an example of a misnomer). History ...

, metal foil made of tin, the direct predecessor to aluminium foil *

Transparency (projection) A transparency, also known variously as a viewfoil or foil (from the French word "feuille" or sheet), or viewgraph, is a thin sheet of transparent flexible material, typically polyester (historically cellulose acetate), onto which figures can be ...

, a thin sheet of transparent flexible material, placed on an overhead projector for display to an audience

Fluid dynamics

Foil (fluid mechanics) A foil is a solid object with a shape such that when placed in a moving fluid at a suitable angle of attack the lift (force generated perpendicular to the fluid flow) is substantially larger than the drag (force generated parallel to the fluid fl ...

Airfoil An airfoil (American English) or aerofoil (British English) is a streamlined body that is capable of generating significantly more Lift (force), lift than Drag (physics), drag. Wings, sails and propeller blades are examples of airfoils. Foil (fl ...

, a foil operating in air **

Hydrofoil A hydrofoil is a lifting surface, or foil, that operates in water. They are similar in appearance and purpose to aerofoils used by aeroplanes. Boats that use hydrofoil technology are also simply termed hydrofoils. As a hydrofoil craft gains sp ...

, a foil operating in water **

Parafoil A parafoil is a nonrigid (textile) airfoil with an aerodynamic cell structure which is inflated by the wind. Ram-air inflation forces the parafoil into a classic wing cross-section. Parafoils are most commonly constructed out of ripstop nylon. T ...

, a non-rigid airfoil, inflated during use *

Foil bearing A foil bearing, also known as a foil-air bearing, is a type of air bearing. A shaft is supported by a compliant, spring-loaded foil journal lining. Once the shaft is spinning fast enough, the working fluid (usually air) pushes the foil away fro ...

, a type of fluid bearing

Arts and culture

Foil (architecture) A foil is an architectural device based on a symmetrical rendering of leaf shapes, defined by overlapping circles of the same diameter that produce a series of cusps to make a lobe. Typically, the number of cusps can be three (trefoil), four (qu ...

, decorative device derived from cusps of circles *

Foil stamping Hot stamping or foil stamping is a printing method of relief printing in which pre-dried ink or foils are transferred to a surface at high temperatures. The method has diversified since its rise to prominence in the 19th century to include a var ...

, a printmaking technique *

Foil (fencing) A foil is one of the three weapons used in the sport of fencing. It is a flexible sword of total length or under, rectangular in cross section, weighing under , with a blunt tip. As with the épée, points are only scored by making contact with ...

, one of the three weapons used in modern fencing *

Foil (fiction) In any narrative, a foil is a character who contrasts with another character, typically, a character who contrasts with the protagonist, in order to better highlight or differentiate certain qualities of the protagonist. A foil to the protagonist ...

, a subsidiary character who emphasizes the traits of a main character ** Comedic or comic foil, the straight man in a comedy

double act A double act (also known as a comedy duo) is a form of comedy originating in the British music hall tradition, and American vaudeville, in which two comedians perform together as a single act, often highlighting differences in their characters' ...

Foil (narrative) In any narrative, a foil is a character who contrasts with another character, typically, a character who contrasts with the protagonist, in order to better highlight or differentiate certain qualities of the protagonist. A foil to the protagonist ...

, a character who contrasts with another character of a narrative work * "Foil" (song), "Weird Al" Yankovic's parody of Lorde's song "Royals"

Navigation

, a type of high-powered motorboat that uses underwater foils to lift its hull above the water when moving at high speeds *

Bruce foil A Bruce foil is a variant of the leeboard, consisting of a foil typically mounted on an outrigger and always set at an angle to provide both lateral and vertical force. It was invented by Edmond Bruce in the early 1960s, and first published in the ...

, a foil used on an outrigger to prevent a boat from heeling *

Centreboard A centreboard or centerboard (US) is a retractable hull appendage which pivots out of a slot in the hull of a sailboat, known as a ''centreboard trunk'' (UK) or ''centerboard case'' (US). The retractability allows the centreboard to be raised t ...

, a movable keel that functions as a foil *

Foilboard A foilboard, also known as a hydrofoil board or foil surfboard, is a type of board used in water sports; it is distinct from surfboards in that it has a hydrofoil rather than fins mounted underneath. This hydrofoil design allows the surfboard and ...

, a surfboard using a hydrofoil

Other uses

* People in a

police lineup A police lineup (in American English) or identity parade (in British English) is a process by which a crime victim or witness's putative identification of a suspect is confirmed to a level that can count as evidence at trial. The suspect, along ...

First-order inductive learner In machine learning, first-order inductive learner (FOIL) is a rule-based learning algorithm. Background Developed in 1990 by Ross Quinlan,J.R. Quinlan. Learning Logical Definitions from Relations. Machine Learning, Volume 5, Number 3, 1990/ref> ...

– a rule-based learning algorithm * The

FOIL method In high school algebra, ''FOIL'' is a mnemonic for the standard method of multiplying two binomials—hence the method may be referred to as the FOIL method. The word ''FOIL'' is an acronym for the four terms of the product: * First ("first ...

, a mnemonic in algebra, to expand the product of two first-degree polynomials ("linear factors") *

FOIL (programming language) FOIL was the name for two different programming languages. CAI style language The first FOIL was a CAI language developed at the University of Michigan in 1967. The acronym stood for File-Oriented Interpretive Language and it was very similar ...

, either of two now-defunct computer programming languages *

Forum of Indian Leftists The Forum of Indian Leftists (FOIL), or the Forum of Inquilabi Leftists, is a group of left-wing activists of Indian background. The organization describes itself as "a clearinghouse for radical Indian activists in the United States, Canada and Eng ...

, a political group of Indian intellectuals *

Freedom of information legislation Freedom of information laws allow access by the general public to data held by national governments and, where applicable, by state and local governments. The emergence of freedom of information legislation was a response to increasing dissatis ...

or Freedom of Information Law (FOIL) *

Ultrasonic foil (papermaking) A paper machine (or paper-making machine) is an industrial machine which is used in the pulp and paper industry to create paper in large quantities at high speed. Modern paper-making machines are based on the principles of the Fourdrinier Machin ...

, a type of high-frequency vibrating foil involved in papermaking * Split tally, in ancient financial accounting, the part of a split tally stick given to the recipient in a transaction *

, a weapon in fencing {{Disambiguation