X, or x, is the twenty-fourth and third-to-last letter in the modern English alphabet and the ISO basic Latin alphabet.
Its  name in English is "ex" (pronounced ), plural exes."
X", Oxford English Dictionary, 2nd edition (1989); Merriam-Webster's Third New International Dictionary of the English Language, Unabridged (1993); "ex", op.
cit.
History
In Ancient Greek, 'Χ' and 'Ψ' were among several variants of the same letter, used originally for  and later, in western areas such as Arcadia, as a simplification of the digraph 'ΧΣ' for .
In the end, more conservative eastern forms became the standard of Classical Greek, and thus 'Χ' (Chi) stood for  (later ; palatalized to  in Modern Greek before front vowels).
However, the Etruscans had taken over 'Χ' from western Greek, and it therefore stands for  in Etruscan and Latin.
The letter 'Χ' ~ 'Ψ' for  was a Greek addition to the alphabet, placed after the Semitic letters along with phi 'Φ' for .
Pronunciation and use
Pronunciations of Xx
English
In English orthography,  is typically pronounced as the voiceless consonant cluster  when it follows the stressed vowel (e.g. ox), and the voiced consonant  when it precedes the stressed vowel (e.g. exam).
It is also pronounced  when it precedes a silent  and a stressed vowel (e.g. exhaust).
Before  or , it can be pronounced  or  (e.g. sexual and luxury); these result from earlier  and .
It also makes the sound  in words ending in -xion.
When  ends a word, it is always  (e.g. fax), except in loan words such as faux (see French, below).
There are very few English words that start with  (the fewest of any letter).
When  does start a word, it is usually pronounced  (e.g. xylophone, xenophobia, and xanthan); in rare recent loanwords or foreign proper names, it can also be pronounced  (e.g. the obsolete Vietnamese monetary unit xu) or  (e.g. Chinese names starting with Xi like Xiaomi or Xinjiang).
Many of the words that start with  are of Greek origin, or standardized trademarks (Xerox) or acronyms (XC).
In abbreviations, it can represent "trans-" (e.g. XMIT for transmit, XFER for transfer), "cross-" (e.g. X-ing for crossing, XREF for cross-reference), "Christ-" as shorthand for the labarum (e.g. Xmas for Christmas, Xian for Christian), the "crys-" in crystal (XTAL), or various words starting with "ex-" (e.g. XL for extra large, XOR for exclusive-or).
X is the third least frequently used letter in English (after  and ), with a frequency of about 0.15% in words.
Other languages
In Latin,  stood for .
In some languages, as a result of assorted phonetic changes, handwriting adaptations or simply spelling convention,  has other pronunciations:
In Basque,  represents .
Additionally there is the digraph  .
In Dutch,  usually represents , except in the name of the island of Texel, which is pronounced Tessel.
This is because of historical sound-changes in Dutch, where all  sounds have been replaced by  sounds.
Words with an  in the Dutch language are nowadays usually loanwords.
In the Dutch-speaking part of Belgium, family names with  are not uncommon (e.g. Dierckx, Hendrickx, Koninckx, Sterckx, Vranckx).
In Norwegian,  is generally pronounced , but since the 19th century, there has been a tendency to spell it out as ; it may still be retained in personal names, though it is fairly rare, and occurs mostly in foreign words and SMS language.
Usage in Danish and Finnish is similar (while Swedish, on the other hand, makes frequent use of  in native words as well as in loanwords).
In German, generally pronounced ; in native words, however,such as Ochs or wachsen,  the cluster  is often written .
, silent (or  in liaison if the next word starts with a vowel).
Three exceptions are pronounced : six ("six"), dix ("ten") and in some city names such as Bruxelles (although some people pronounce it 'ks') or Auxerre; it is fully pronounced  in Aix, the name of several towns.
It is pronounced  in sixième and dixième.
Otherwise  or (primarily in words beginning with ex- followed by a vowel) .
In Italian,  is either pronounced , as in extra, uxorio, xilofono, or , as exogamia, when it is preceded by  and followed by a vowel.
In several related languages, notably Venetian, it represents the voiced sibilant .
It is also used, mainly amongst the young people, as a short written form for "per", meaning "for": for example, "x sempre" ("forever").
This is because in Italian the multiplication sign (similar to ) is called "per".
However,  is found only in loanwords, as it is not part of the standard Italian alphabet; in most words with , this letter may be replaced with 's' or 'ss' (with different pronunciation: xilofono/silofono, taxi/tassì) or, rarely, by 'cs' (with the same pronunciation: claxon/clacson).
In Old Spanish,  was pronounced , as it is still currently in other Iberian Romance languages.
Later, the sound evolved to a hard  sound.
In modern Spanish, due to a spelling reform, whenever  is used for the  sound it has been replaced with , including in words that originally had  such as ejemplo or ejercicio, though  is still retained for some names (notably 'México', even though 'Méjico' may sometimes be used in Spain).
Presently,  represents the sound  (word-initially), or the consonant cluster  (e.g. oxígeno, examen).
Rarely, it can be pronounced  as in Old Spanish in some proper nouns such as 'Raxel' (a variant of Rachel) and Uxmal.
In Galician and Leonese,  is pronounced  in most cases (often used in place of etymological g or j).
The pronunciation  occurs in learned words, such as 'taxativo' (taxing).
However, Galician speakers tend to pronounce it , especially when it appears before plosives, such as in 'externo' (external).
In Catalan,  has three sounds; the most common is ; as in 'xarop' (syrup).
Other sounds are: ; 'fixar' (to fix), ; 'examen'.
In addition,  gets voiced to  before voiced consonants; 'caixmir'.
Catalan also has the digraph , pronounced .
In Portuguese,  has four main sounds; the most common is , as in 'xícara' (cup).
The other sounds are:  as in 'flexão' (flexion); , when preceded by E and followed by a consonant, as in 'contexto' ( in European Portuguese), and in a small number of other words, such as 'próximo' (close/next); and (the rarest) , which occurs in the prefix 'ex-' before a vowel, as in 'exagerado' (exaggerated).
A rare fifth sound is , coexisting with  and  as acceptable pronunciations in exantema and in words with the Greek prefix 'hexa-'.
In Sardinian and Ligurian, X represents .
In Venetian, it represents the voiced alveolar sibilant  much like in Portuguese 'exagerado', English 'xylophone' or in the French 'sixième'.
Examples from medieval texts include raxon (reason), prexon (prison), dexerto (desert), chaxa/caxa (home).
Nowadays, the best-known word is xe (is/are).
The most notable exception to this rule is the name Venexia  in which  has evolved from the initial voiced sibilant  to the present day voiceless sibilant.
In Albanian,  represents , while the digraph  represents .
In Maltese,  is pronounced  or, in some cases,  (only in loanwords such as 'televixin', and not for all speakers).
In Polish,  was used prior to 19th century both in loanwords and native words and was pronounced  or , e.g. xiążę, xięstwo (now książę, księstwo).
Later was replaced by  and  in almost all words and remained only in a few loanwords as 'xenia' (xenien), surnames as Axentowicz, Jaxa, Koxowski, Mixtacki, Rexemowski, Xiężopolski, names as Xawery, Xymena and abbreviations.
Additionally, in languages for which the Latin alphabet has been adapted only recently,  has been used for various sounds, in some cases inspired by European usage, but in others, for consonants uncommon in Europe.
For these no Latin letter stands out as an obvious choice, and since most of the various European pronunciations of  can be written by other means, the letter becomes available for more unusual sounds.
represents  (voiceless velar fricative) in e.g. Azerbaijani, Kurdish (Hawar alphabet), Georgian (when Latinized), Lojban, Pashto (when Latinized), Tatar (Jaꞑalif, Zamanälif, official romanization of 2012), Uzbek, and Uyghur (Latin script).
Esperanto: The x-convention replaces , , , , , and  with x-suffixes: , , , , , and .
In transliteration of Indian languages, primarily Indo-Aryan languages,  represents the consonant cluster  in alternate spellings of words containing 'क्ष' (kṣ), especially names such as Laxmi and Dixit.
Less frequently,  is used to represent 'ख़' .
In Apache  represents
In Nahuatl,  represents .
In Nguni languages,  represents the alveolar lateral click .
In Pirahã,  symbolizes the glottal stop .
An illustrating example of "x" as a "leftover" letter is differing usage in three different Cushitic languages:
Afar: voiced alveolar implosive
Oromo: alveolar ejective
Somali: voiceless pharyngeal fricative
In East and Asia:
In Lao, based on romanization of Lao consonants,  may represent , e.g. in Lan Xang.
In Vietnamese,  is pronounced like English  (at the beginning of a word, e.g. "sing").
This sound was  in Middle Vietnamese, resembling the Portuguese sound , spelled .
In Hanyu Pinyin, Standard Chinese's official transcription system in China, Malaysia, Singapore, and Taiwan, the letter  represents the voiceless alveolo-palatal fricative , for instance in 'Xi', .
Other systems
In the International Phonetic Alphabet,  represents a voiceless velar fricative.
Other uses
In mathematics, x is commonly used as the name for an independent variable or unknown value.
The modern tradition of using x, y and z to represent an unknown (incognita) was introduced by René Descartes in La Géométrie (1637).
See History of algebra.
As a result of its use in algebra, X is often used to represent unknowns in other circumstances (e.g. X-rays, Generation X, The X-Files, and The Man from Planet X; see also Malcolm X).
On some identification documents, the letter X represents a non-binary gender, where F means female and M means male.
In the Cartesian coordinate system, x is used to refer to the horizontal axis.
It is also sometimes used as a typographic approximation for the multiplication sign, .
In mathematical typesetting, x meaning an algebraic variable is normally in italic type (x\!), partly to avoid confusion with the multiplication symbol.
In fonts containing both x (the letter) and × (the multiplication sign), the two glyphs are dissimilar.
It can be used as an abbreviation for 'between' in the context of historical dating; e.g., '1483 x 1485'.
Maps and other images sometimes use an X to label a specific location, leading to the expression "X marks the spot".
The Roman numeral X represents the number 10.
In art or fashion, the use of X indicates a collaboration by two or more artists, e.g. Aaron Koblin x Takashi Kawashima.
This application, which originated in Japan, now extends to other kinds of collaboration outside the art world.
This usage mimics the use of a similar mark in denoting botanical hybrids, for which scientifically the multiplication × is used, but informally a lowercase "x" is also used.
In text language, at the end of a letter or at the end of an email 'x' can mean a kiss.
An X rating denotes media such as movies that are intended for adults only.
Related characters
Descendants and related characters in the Latin alphabet
X with diacritics: Ẍ ẍ Ẋ ẋ X̂ x̂ ᶍ
IPA-specific symbols related to X:
Teuthonista phonetic transcription-specific symbols related to X:
ˣ : Modifier letter small x is used for phonetic transcription
ₓ : Subscript small x is used in Indo-European studies
Ancestors and siblings in other alphabets
Χ χ : Greek letter Chi, from which the following derive:
Х х : Cyrillic letter Kha
: Coptic letter Khe, which derives from Greek Chi
: Gothic letter enguz, which derives from Greek Chi
𐌗 : Old Italic X, which derives from Greek Chi, and is the ancestor of modern Latin X
: Runic letter Gyfu, which may derive from old Italic X
Ξ ξ : Greek letter Xi, which was used in place of Chi in the Eastern (and the modern) Greek alphabets
Computing
Computing codes
1
In the C programming language, "x" preceded by zero (as in 0x or 0X) is used to denote hexadecimal literal values.
X is commonly used as a prefix term in nouns related to the X Window System and Unix.
Other representations
See also
X mark
References
External links
