F (named ef , as a verb spelled eff) is the sixth letter in the ISO basic Latin alphabet.

The article is about the newer independent festival, held in February. For the older festival, held in April, see Istanbul International Film Festival.

AFM International Independent Film Festival, more commonly known as !f Istanbul is an annual, international film festival dedicated to independent films from all around the world. The festival is held each year in mid-February at AFM Theaters, hence its name, in Istanbul, Turkey, with a partial showcase in Ankara.

F+ may refer to:

• F+ (pitch), a musical pitch traditionally used for the Northumbrian smallpipes
• F⁺ a bacterium having F-plasmid in bacterial conjugation
• In Academic grading in the United States, F+ is a rarely used grade above F.

Feminist Initiative (, abbreviated Fi or F!) is a feminist political party in Sweden. The party was formed (from a previous pressure group of the same name) in 2005 and announced on 9 September 2005 that it would put up candidates for the 2006 parliamentary elections in Sweden. They got around 0.68% of the votes, meaning they didn't pass the 4% threshold necessary to enter the Riksdag.

Fluoride is the anion F^-, the reduced form of fluorine when as an ion and when bonded to another element. Both organofluorine compounds and inorganic fluorine containing compounds are called fluorides. Fluoride, like other halides, is a monovalent ion (-1 charge). Its compounds often have properties that are distinct relative to other halides. Structurally, and to some extent chemically, the fluoride ion resembles the hydroxide ion. Fluorine-containing compounds range from potent toxins such as sarin to life-saving pharmaceuticals such as efavirenz, and from inert materials such as sulfur hexafluoride to the highly reactive chlorine trifluoride. The range of fluorine-containing compounds is vast because fluorine is capable of forming compounds with all the elements except helium and neon.

The Fourier transform expresses a mathematical function of time as a function of frequency, known as its frequency spectrum. Named for Joseph Fourier, it is a mathematical transform with many applications in physics and engineering. The Fourier integral theorem details this relationship. For instance, the transform of a musical chord made up of pure notes (without overtones) expressed as amplitude as a function of time, is a mathematical representation of the amplitudes and phases of the individual notes that make it up. The function of time is often called the time domain representation, and the frequency spectrum the frequency domain representation. The inverse Fourier transform expresses a frequency domain function in the time domain. Each value of the function is usually expressed as a complex number (called complex amplitude) that can be interpreted as a magnitude and a phase component. The term "Fourier transform" refers to both the transform operation and to the complex-valued function it produces.

"Fuck" is an English word that is almost universally considered vulgar by its speakers. In its most literal meaning, it refers to the act of sexual intercourse. By extension it may be used to negatively characterize anything that can be dismissed, disdained, , or destroyed and may also be used as an intensive.

Fuck (styled as FUCK, F★CK or F*CK) is a 2005 documentary by director/producer Steve Anderson and Rainstorm Entertainment about the social, political, personal, historical, linguistic and artistic significance of the word fuck. It features commentary by a variety of individuals, including linguists, comedians, artists, musicians, filmmakers, authors, porn stars, politicians, and media personalities as well as clips from George Carlin, Scarface, Country Joe and the Fish's Woodstock performance, President George W. Bush's one-fingered salute to a camera, various Lenny Bruce performances, U2's Golden Globe acceptance, Paul Robert Cohen's protest and Nipplegate, accompanied with animated segues created by Bill Plympton. The movie was shown for the first time on November 7, 2005 at the AFI Film Festival.

L-fuculokinase is an enzyme that catalyzes the chemical reaction

PHI is a three-letter acronym or abbreviation that can refer to:

• Packard Humanities Institute
• Paraprofessional Healthcare Institute, a nonprofit organization based in New York City
•  Pepco Holdings Inc.
• Post-Polio Health International
• Protected Health Information as part of the HIPAA regulations
• The Philippines IOC country code
• Philadelphia, Pennsylvania
  • Philadelphia Phillies, a Major League Baseball team
  • Philadelphia Flyers, a National Hockey League team
  • Philadelphia Eagles, a National Football League team
  • Philadelphia 76ers, a National Basketball Association team
• Peptide Histidine Isoleucine

Phi (uppercase Φ, lowercase φ, or math symbol ), pronounced or sometimes in English, and in modern Greek, is the 21st letter of the Greek alphabet. In modern Greek, it represents , a voiceless labiodental fricative. In Ancient Greek it represented , an aspirated voiceless bilabial plosive (from which English ultimately inherits the spelling "ph" in words derived from Greek). In the system of Greek numerals it has a value of 500 (φʹ) or 500,000 (͵φ). The Cyrillic letter Ef (Ф, ф) arose from Φ.