F (named ef ) is the sixth letter in the modern English alphabet and the ISO basic Latin alphabet.

F is the sixth letter of the Latin alphabet.

F* may refer to:

• Fuck (film)
• F* (programming language)

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.

Fluoride , is an inorganic, monatomic anion of fluorine with the chemical formula . Fluoride is the simplest anion of fluorine. Its salts and minerals are important chemical reagents and industrial chemicals, mainly used in the production of hydrogen fluoride for fluorocarbons. In terms of charge and size, the fluoride ion resembles the hydroxide ion. Fluoride ions occur on earth in several minerals, particularly fluorite, but are only present in trace quantities in water. Fluoride contributes a distinctive bitter taste. It contributes no color to fluoride salts.

The Fourier transform performs a decomposition of a function of into its sinusoidal components. As typically phrased in the language of signal processing, the transformation decomposes a signal – some given function of time – into the frequencies that make up the signal, akin to how a musical chord can be expressed as combination of its constituent notes. While the Fourier transform is not limited to functions of time in the literal sense, it is conventional to call the domain of the original function the time domain and the domain of the transformed function the frequency domain.

Fuck is an obscene English language word, which refers to the act of sexual intercourse and is also commonly used as an intensifier or to denote disdain. Its origin is obscure but is usually considered to be first attested to around 1475, although it may be considerably older. In modern usage, the term fuck and its derivatives (such as fucker and fucking) can be used as a noun, a verb, an adjective, an interjection, or an adverb. There are many common phrases that employ the word, as well as compounds that incorporate it, such as motherfucker and .

L-fuculokinase is an enzyme that catalyzes the chemical reaction

Phi (uppercase Φ, lowercase or ; , pheî, ; modern , fi, ; English: ) is the 21st letter of the Greek alphabet. In Ancient Greek, it represented an aspirated voiceless bilabial plosive , which was the origin of its usual romanization as "ph". In modern Greek, it represents a voiceless labiodental fricative  and is correspondingly romanized as "f". Its origin is uncertain but it may be that phi originated as the letter qoppa and initially represented the sound before shifting to Classical Greek . In traditional Greek numerals, phi has a value of 500 or . The Cyrillic letter Ef (Ф, ф) descends from phi.

Phi (uppercase Φ, lowercase φ, or math symbol ϕ) is the 21st letter of the Greek alphabet.