X

For other uses, see X (disambiguation)}}}.

Latin alphabet
	Aa	Bb	Cc	Dd
Ee	Ff	Gg	Hh	Ii	Jj
Kk	Ll	Mm	Nn	Oo	Pp
Qq	Rr	Ss	Tt	Uu	Vv
	Ww	Xx	Yy	Zz

The letter X is the twenty-fourth letter in the Latin alphabet. Its name in English is ex (/ɛks/).

In phonetics, x is the IPA and X-SAMPA symbol for the voiceless velar fricative (IPA is used for pronunciation throughout this article).

Contents

1 History
2 Usage
3 Codes for computing
4 Meanings for X
5 See also

History

The consonant cluster /ks/ was, in Ancient Greek, written as either Chi Χ (Western Greek) or Xi Ξ (Eastern Greek). In the end, Chi was standardized as /kʰ/ (/x/ in Modern Greek), while Xi was standardized for /ks/. But the Etruscans had taken over Χ from older Western Greek; therefore, it stood for /ks/ in Etruscan and Latin.

It is unknown whether the letters Chi and Xi are Greek inventions, or whether they are ultimately of Semitic origin. Chi was placed toward the end of the Greek alphabet, after the Semitic letters, along with Phi, Psi, and Omega, suggesting that it was an innovation; further, there is no letter corresponding specifically to the sound /ks/ in Semitic. There was a Phoenician letter 15px kheth with a probable sound /ħ/, somewhat similar to /kʰ/, but this was adopted into Greek as first the consonant /h/, and later, the long vowel Eta (Η,η), and does not seem to have been the source of Greek Chi. The Phoenician letter 15px Samekh (representing /s/) is usually considered the inspiration for Greek Xi, but as noted, Chi had a graphically distinct shape from Xi — although it may possibly have been another variant originally based on samekh. The original form of samekh may have been an Egyptian hieroglyph for the Djed column, but this too is uncertain, as no intervening Proto-Sinaitic form of this letter is attested.

Egyptian hieroglyph "column" Phoenician S Greek Xi Greek Chi Etruscan X
R11

Egyptian hieroglyph "column"	Phoenician S	Greek Xi	Greek Chi	Etruscan X
R11

Usage

In some languages, as a result of assorted phonetic changes and handwriting adaptations, X has other pronunciations:

Basque: as a spelling for [ʃ].
English: X is a double consonant or, rather, a superfluous sign for the compound consonants [ks]; or sometimes when followed by an accented syllable beginning with a vowel, or when followed by silent h and an accented vowel [gz] (e.g. exhaust, exam); usually [z] at the beginnings of words (e.g. xylophone), and in some compounds keeps the [z] sound, as in (e.g. meta-xylene). It also makes the sound [kʃ] in instances of -xion which is usually spelt -ction (such as connexion, reflexion, inflexion et cetera) but only occurs in British English. It can also represent the sound [gʒ] or [kʃ], for example, in the word luxury, sexual. Final x is always [ks] (e.g. ax/axe).
French: at the ends of words, silent (or [z] in liaison if the next word starts with a vowel). This usage arose as a handwriting alteration of final -us.
Spanish: In old Spanish, X was pronounced like [ʃ] as it is still currently in other Iberian languages. Later, the sound evolved to a hard [x] sound. In modern Spanish, the hard [x] sound is spelled with a j, though x is still retained for some names (notably México, which alternates with Méjico). Now, X represents the sound [s] (word-initially), or the consonat clusters [ks] and [gs] (e.g. oxígeno, examen). In American and seseo Spanish, the xc in excelente is pronounced as [ks-s] but in Spain, as an official rule, this combination is pronounced [ks-θ].
In Galician it represents [ʃ].
Portuguese: as a spelling for [ʃ] or [ks], usually.
Nguni languages: represents the Lateral alveolar click [ǁ].
In some recently created alphabets based on the Roman alphabet, x represents [x]. This is the case in Kurdish, Azeri, Uzbek, Tatar and Lojban.
In Hanyu Pinyin, the official transcription system for Mandarin Chinese, the letter x denotes the voiceless alveolo-palatal fricative /ɕ/.
In the German and Italian languages, X is used mainly in foreign loan words.

No words in the Basic English vocabulary begin with X, but it occurs in words beginning with other letters.

Codes for computing

Alternative representations for X

NATO phonetic		Morse code
X-ray		[–··–]

Signal flag	Semaphore	ASL Manual	Braille

In Unicode the capital X is codepoint U+0058 and the lowercase x is U+0078.

The ASCII code for capital X is 88 and for lowercase x is 120; or in binary 01011000 and 01111000, correspondingly.

The EBCDIC code for capital X is 231 and for lowercase x is 167.

The numeric character references in HTML and XML are "X" and "x" for upper and lower case respectively.

Meanings for X

In a general sense, X represents a generic placeholder variable, whose value is unknown or secret but within a set defined by context, 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 (see X (anime)) which has also been adapted into a 1996 feature film and a 2001 television series.
In astronomy,
* Planet X is a hypothetical planet in the Solar System beyond the orbit of Pluto.
* X stands for a comet of unknown orbit, as in X/1106 C1, one of whose fragments is thought to have been the Great September Comet of 1882.
* X stands for a December 1 through 15 discovery, in the provisional designation of a comet (e.g. C/1927 X1, Comet Skjellerup-Maristany) or asteroid (e.g. (3757) 1982 XB).
On ballots in the form of boxes printed on paper to make a mark in, the symbol used in the West to indicate one's choice is often in the form of an X and is so called. This extends to similar boxes on paper. However, in Japan and Korea, boxes have a circle drawn in them to indicate one's choice, while those which are rejected are marked with an X.
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 chemistry, X is used to represent a halogen atom or ion. This is generally used to represent any halogen in a general formula demonstrating reactions or compounds common to all halogens and is used instead of the symbol for the element.
In clothing, X is used as an abbreviation for extra, such as XXL for extra-extra-large or XS for extra-small.
In computing:
* X is the name of a free graphical windowing system developed at MIT and standard on Unix-like (including Linux); see X Window System.
* In Windows, Ctrl-X, and in Mac OS, Command-X, removes the selected text, image or sound and places it on the clipboard. This is referred to as cutting.
* 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 an ITU-T series of recommendations on Data networks and open system communication and used in their names such as X.509. See .
* x is the repetition operator in Perl programming language.
In economics, especially national income accounting, X is usually used to represent exports.
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), due to its Greek name.
*X is used in an alternative spelling of some names, for example Christina = Xtina
*X is an abbreviation for cross in words like "Xing" (crossing) and "Kings X" (Kings Cross).
*X is an abbreviation for trans in words like "Xfer" (transfer) and "Xmit" (transmit)
*X also appears in other jargon or trade abbreviations, such as "xtal" (Crystal), "xant" (chrysanthemum), "reXn" or "rxn" (reaction), "Xlation" (translation), "SXSW" (South by Southwest festival), "Rx" (receive) or (recrystallized) , "Tx" (transmit), "Dx" (distance).
* In Online computer game MMORPG trading of currencies such as in World of Warcraft; "xmute" meaning to transmute an item into another more powerful or more valuable item.
* In American slang, X is often used as an abbreviation of ecstasy (MDMA), a synthetic drug.
*In written communication, X can be paired with the letter O to convey a warm sentiment (traditionally Hugs and Kisses) and is typically used as a closing, e.g. "XO, Bob".
In Erotic art, usually H Manga, an X inbetween two names would denote that those two characters would be lovers.
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 both JFK and The X-Files, X is the name of a mysterious informant who supplies the main character with information regarding a government conspiracy.
In finance, X is the U.S. ticker symbol for United States Steel Corporation.
In French education, X is a nickname for the École Polytechnique and its alumni.
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 the Middle Ages, this represented a cross and so signified a Christian signatory, whereas illiterate Jews used a circle (kikel).
In mathematics:
* [\mathit] commonly represents an unknown variable. Even though any letter can be used, [\mathit] 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 [\mathit]. (Spanish pronunciation of "x" has changed since.) But some sources say that this [\mathit] is an abbreviation of Latin causa which was a translation of Arabic شيء. That started the habit of using letters to represent quantities in algebra.
* [\mathit] is the usual symbol for the variable represented on the horizontal axis (ordinate) in analytic geometry.
* X means 10 in Roman numbers.
* The symbol [\times] (×), similar to the lowercase x, denotes multiplication.
In military science, X is the US Navy hull classification symbol for Submersible Craft.
In optics, an x marks the magnification of a lens or instrument. A 2x lens shows an image twice bigger than reality.
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 performed and written by the rapper Xzibit. X is also his most common short nickname, which comes from yet another nickname, X to the Z.
* see X (album) for albums entitled "X"
* see the "X" section of List of sets of unrelated songs with identical titles for songs entitled "X"
* see X (band) for bands named "X"
As the first letter of a postal code:
* In Canada, X stands for Nunavut and the Northwest Territories.
In publishing, X is used in ISBN and ISSN numbers as an eleventh one-digit numeral, following 9.
X is a roller coaster at Six Flags Magic Mountain.
In Roman numerals, X denotes ten (there are also separate Unicode characters for this number, 0x2169 "Ⅹ" and 0x2179 "ⅹ").
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 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 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.
*In Metroid Fusion, X is the name for the parisitic aliens which are the main conflict in the game.
X is the bassist of the band Audeo
X is a common nickname for St. Francis Xavier University in Antigonish, Nova Scotia. The school is also famous for the X-Ring, a gold ring with a large black X, worn by its graduates.
Charlie Manson, and some of his followers, carved an X into their foreheads to show that they have "X'ed" themselves out of this world.
X is also used as a denomination for "prototype" in the anime Mobile Suit Gundam SEED.
X is sometimes called the most mysterious of all of the alphabet, next to or above the letter Z. The letter X has been put into many words to make them sound "cool", as in the "X" team, "X"-men, or agent "X". X has appeared in anime on a variety of character's faces or on animals, as seen in the anime dragon Ball and the Fullmetal Alchemist character Scar
In , Planet X is a mysterious X-ringed purple mechanical planet that is the home of Sideways and Soundwave.
In the Powerpuff Girls, Chemical X is the main ingredient to create them.

X

History

Usage

Codes for computing

Meanings for X

See also