X

X is the twenty-fourth letter of the Latin alphabet. In phonetics, is the IPA and X-SAMPA symbol for the voiceless velar fricative. The IPA is used here.

Meanings for X

• In a general sense, X represents an unknown or secret, as in project X or mister X. This usage is borrowed from mathematics (see below) and acquired some specialized meanings, listed here.
• Members of the Nation of Islam change their surnames to "X" to symbolize that their African names were lost in slavery, an example is Malcolm X.
• In aeronautics, X is the designation given to an experimental aircraft of the US government, for instance, the X-1 rocketplane that first broke the sound barrier. It is also a prefix to experimental types of US military aircraft, for instance, the XB-70.
• In anime, X is a series produced by CLAMP based on the Japanese manga X/1999 (see X (anime)) which has also been adapted into a 1996 feature film and a 2001 television series.
• In art, X alludes to the infinite joy of creation.
• In astronomy, Planet X is a hypothetical planet in the Solar System beyond the orbit of Pluto.
• In beverages, X is a symbol for an alcoholic proof of 50; multiple Xes indicate multiples of 50.
• In cabalistic philosophy, X references both birth and death.
• In clothing, X is used as an abbreviation for extra, such as XXL for extra-extra-large or XM for extra-medium.
• In computing:
• In Windows, Ctrl-X, and Mac OS, Command-X, removes the selected text, image or sound and places it on the clipboard.
• X is the name of a free graphical windowing system developed at MIT and standard on Unix and Linux; see X Window System.
• X is often used as a symbol of multiplication, as in denoting the spin (and, later, transfer) speed of CDs and DVDs compared to an original standard speed. This usage is a corruption of the multiplication symbol *. The data transfer speed for 1X CDs is 153,600 bytes/second; for 1X DVDs it is 1,385,000 bytes/second (approximately 9.02 times faster).
• X is used as an abbreviation for the Apple operating system Mac OS X.
• x is the repetition operator in Perl programming language.
• In French education, X is a nickname for the École Polytechnique.
• In electrical engineering, X is the symbol for reactance.
• In English:
• X is an abbreviation for Christ, as in Xmas (Christmas), X(t)ian (Christian), and Xianity (Christianity).
• X is a symbol for a kiss, as in love notes. (See Hugs and Kisses.)
• X is an abbreviation for cross in words like "Xing" (crossing) and "Kings X" (Kings Cross).
• X also appears in other jargon or trade abbreviations, such as "xtal" (Crystal), "xant" (chrysanthemum), "reXn" (reaction), "Xlation" (translation), "SXSW" (South by Southwest Festival), "Rx" (receive), "Tx" (transmit), "Dx" (distance).
• In American slang, X is often used as an abbreviation of ecstasy (MDMA), a synthetic drug.
• to sign with a cross (often for illiteracy).
• In film:
• X is a rating given to films suitable for an adult-only audience; see X-rated. NC-17 has replaced the X rating in the U.S.. The UK replaced the X rating with the 18 certificate. Australia retains the X rating.
• X is the title of a 1928 German film; see X (film)
• The X-Files was a popular 1990s American science fiction television series.
• In finance, X is the U.S. ticker symbol for United States Steel Corporation.
• In games, X is representation for a cross in games like tic tac toe (naughts and crosses)
• In genetics, X denotes the X chromosome.
• In sex, XX denotes female in the XY sex-determination system.
• In legal documents, X can stand for the signature of an illiterate signatory, as long as the document is countersigned by a literate witness.
• In mathematics:
• x commonly represents an unknown variable. Even though any letter can be used, x is the most common by far. This usage can be traced back to the Arabic word šay' شيء = "thing", which in translated algebra texts and similar was taken into Old Spanish with the pronunciation "šei", which was written xei, which was soon habitually abbreviated to x. But some sources say that this x is an abbreviation of Latin causa which was a translation of Arabic شيء. (Spanish pronunciation of "x" has changed since.) That started the habit of using letters to represent quantities in algebra.
• x is the usual symbol for the variable represented on the horizontal axis (ordinate) in analytic geometry.
• X means 10 in Roman numbers.
• The symbol ×, similar to the lowercase x, denotes multiplication.
• In military science, X is the US Navy hull classification symbol for Submersible Craft.
• In philosophy, X may mean the supreme singular guiding principle, the logos, for some people. Especially for skeptics, some of whom have a principle which they don't want to name or are unsure of, or want to be neutral and not to take any side, they use the general letter X to denote their principle.
• In photography, X denotes exact time in flash synchronization.
• In physics, the X-ray is a form of electromagnetic radiation.
• In popular music:
• X is a song by System of a Down.
• X is the name of a Los Angeles punk rock band (see X (US band)).
• X is the name of an Australian punk rock band (see X (Australian band)).
• X was the initial name of the Japanese visual kei rock band X Japan.
• X is the name of several albums by various artists (see X (album)).
• As the first letter of a postal code:
• In Canada, X stands for Nunavut and the Northwest Territories.
• In U.S. politics, X is the pseudonym of the person who blew the whistle on the Watergate crisis.
• In U.S. public policy, X is the author (George F. Kennan) of the X article published in Foreign Affairs.
• In Roman numerals, X denotes ten (there are also separate Unicode characters for this number, 0x2169 "?" and 0x2179 "?").
• In semiotics, an X over something denotes elimination, prohibition or erasure.
• In sociology, X denotes Generation X.
• X is a symbol worn on the hand to denote that someone is straight edge. It is also frequently tattooed on other parts of the body, or worn on clothing, sometimes in triplicate (XXX). Straight-edgers frequently also append Xs to their names, i.e. write their names with Xs, such that 'Jack' would be written XjackX. Straight edge itself is commonly abbreviated to 'sxe' (S.E. with an X in the middle).
• In superhero comic books, an X usually denotes a connection to the popular X-Men franchise, especially when used as a prefix.
• In treasure-hunting, X is used to designate the location of treasure, i.e. X marks the spot.
• In video games:
• X is the bottom of the four face buttons on the original Sony PlayStation controller and the DualShock series of controllers.
• X is the name of the main character in the Mega Man spinoff series, Mega Man X.
• X is a rollercoaster at Six Flags Magic Mountain.
• In economics, X is usually used to represent exports.