X is the twenty-fourth letter in the modern Latin alphabet. Its name in English is spelled ex or ecks (),"X" Oxford English Dictionary, 2nd edition (1989); Merriam-Webster's Third New International Dictionary of the English Language, Unabridged (1993); "ex," op. cit. plural exes.

History

The consonant cluster was, in Ancient Greek, written as either Chi ? (Western Greek) or Xi ? (Eastern Greek). In the end, Chi was standardized as ( in Modern Greek), while Xi was standardized for . But the Etruscans had taken over ? from older Western Greek; therefore, it stood for 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 kheth with a probable sound , somewhat similar to , but this was adopted into Greek as first the consonant /h/, and later, the long vowel Eta (?,?), and does not seem to have been the source of Greek Chi. The Phoenician letter 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.

Usage

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

• Basque: as a spelling for .
• Dutch: The island of Texel is pronounced as Tessel. This is because ss was written with a ligature closely resembling the x.
• English: X is a double consonant or, rather, a sign for the compound consonants ; or sometimes when followed by an accented syllable beginning with a vowel, or when followed by silent h and an accented vowel (e.g. exhaust, exam); usually at the beginnings of words (e.g. xylophone), and in some compounds keeps the sound, as in (e.g. meta-xylene). It also makes the sound in words ending in -xion (typically used only in British-based spellings of the language; American spellings tend to use -ction). It can also represent the sounds or , for example, in the words luxury and sexual, respectively. When the letter X begins a word in the English language such as xynene and a z sound is created the X is said to be silent. Final x is always (e.g. ax/axe) except in loan words such as faux (see French, below). Frequently, it is also exchanged for the letters 'cks' such as in Dix (Dicks), and sux (sucks).
• French: at the ends of words, silent (or in liaison if the next word starts with a vowel). This usage arose as a handwriting alteration of final -us. Two exceptions are pronounced [11]: six and dix.
• In Italian, X is always , as in the words uxorio, extra, xilofono. It is also used, mainly amongst younger generations as a short form for "per" meaning "for", for example, x sempre (forever).
• In Norwegian, X is generally pronounced , but since the nineteenth century there has been a tendency to spell it out as ks whenever possible; it may still be retained in names of people, though it is fairly rare, and occurs mostly in foreign words and SMS language.
• Spanish: In Old Spanish, X was pronounced , as it is still currently in other Iberian languages. Later, the sound evolved to a hard sound. In modern Spanish, the hard sound is spelled with a j, or with a g before e and i, though x is still retained for some names (notably México, which alternates with Méjico). Now, X represents the sound (word-initially), or the consonat clusters and (e.g. oxígeno, examen). Even rarer; like in Old Spanish, the x can be pronounced as in modern day in some proper nouns such as Raxel (a variant of Rachel) and Xelajú. In American and seseo Spanish, the xc in excelente is pronounced as but in Spain, this combination is pronounced .
• In Albanian, x represents , while the digraph xh represents .
• Polish doesn't use X. In loanwords, X is either replaced by ks like in 'ekstra' (extra), or gz like in 'egzotyczny' (exotic).
• Nguni languages: represents the Lateral alveolar click .
• In some recently created alphabets based on the Roman alphabet, x represents . This is the case in Kurdish, Azerbaijani, Uzbek, Tatar and Lojban.
• In Hanyu Pinyin, the official transcription system for Mandarin Chinese, the letter x denotes the voiceless alveolo-palatal fricative .
• In the German and Italian languages, X is used mainly in foreign loan words.
• In Maltese x is pronounced

No words in the Basic English vocabulary begin with X, but it occurs in words beginning with other letters. It is often found in a word with an E before it. Otherwise it is the third most rarely used letter in the English language.

The letter 'X' takes approximately 7% more energy to vocalise over any other letter of the English alphabet (with K and V coming a close 2nd and 3rd respectively).

Codes for computing

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.

Other uses for the letter X

Similar non-Latin letters

• ? : Greek letter Chi
• ? : Cyrillic Kha
• ? : Me (Japanese katakana character)
• ? (Hebrew aleph) sometimes looks like X when handwritten.
• ? : A Japanese or Chinese character usually used in names, pronounced as "Ai".
• In pre-Norman Britain a "?" (Gyfu) was a letter in the Anglo-Saxon Futhorc runic alpabet and also indicated a gift.

Non-letter symbols in Unicode

• × : multiplication sign
• ? : box drawings left diagonal cross
• : multiplication x
• : ballot x
• : heavy ballot x
• × : vector or cross product

Other uses

• A colloquial name for the drug MDMA (derived from another of the drug's nicknames, ecstasy or XTC)
• A placeholder or modifier in usernames (e.g. MagmaX or ixamxthexmaster)
• In genetics, the X chromosome
• A strike in baseball or bowling
• Denotes infantry on military maps
• Marks a mountain summit on topographic maps, such as printed by the USGS
• In American football schematics, a member of the defensive squad
• In ASCII tab, a muted or unplayed guitar string
• In musical notation, a double sharp, raising a note by one full step
• In electronic circuit diagrams, an unused pin of a chip, or, in a circle, a lamp
• Short for "cross", including such abbreviations as "lax" for "lacrosse", or "x-country" for "cross country"
• Generally speaking, Americans do not refer to a lone "x" as a cross, where as this usage does occur outside of the U.S., such as in the name noughts and crosses, which Americans call tic-tac-toe.
• In the U.S., pedestrian crossings are usually marked with "XING".
• The roman numeral for ten, X
• Marks the spot, as on a map of buried treasure
• Experimental, as in X-plane
• Christ, as in Xmas
• In the following entry in the Devil's Dictionary by Ambrose Bierce: "In the algebra of psychology, X stands for woman's mind."
• In several computer operating systems, the button that closes a window is labelled X. Consequently, "to X" can be a verb meaning to close a window. (e.g. "Please X out Microsoft Word".)
• In algebra, X is very commonly associated with an unknown variable. Its first time use is attributed to Omar Khayyám in his Treatise on Demonstration of Problems of Algebra (1070).
• The X axis means the horizontal axis in graphs.
• In France "L'X" is the nickname of the prestigious engineer school Polytechnique
• In the MPAA rating system, X used to indicate an adults-only film. The rating, which was not trademarked, is now widely used to denote pornographic films.
• In computing, X can stand for the X Window System.