X

For the multiplication sign, see ×. For other uses, please see X (disambiguation).

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

X (named ex /ˈɛks/, plural exes^[1]) is the twenty-fourth letter in the ISO basic Latin alphabet. In Roman numerals, it represents 10.

History

In Ancient Greek, 'Χ' and 'Ψ' were among several variants of the same letter, used originally for /kʰ/ and later, in western areas such as Arcadia, as a simplification of the digraph 'ΧΣ' for /ks/. In the end, more conservative eastern forms became the standard of Classical Greek, and thus 'Χ' (Chi) stands for /kʰ/ (later /x/). However, the Etruscans had taken over 'Χ' from western Greek, and it therefore stands for /ks/ in Etruscan and Latin.

The letter 'Χ' ~ 'Ψ' for /kʰ/ was a Greek addition to the alphabet, placed after the Semitic letters along with phi 'Φ' for /pʰ/. (The variant 'Ψ' later replaced the digraph 'ΦΣ' for /ps/; omega was a later addition)..

Greek Chi	Etruscan :X

Use in English

In English orthography, x is typically pronounced as the voiceless consonant cluster /ks/ when it follows the stressed vowel (e.g. ox), and the voiced consonant /ɡz/ when it precedes the stressed vowel (e.g. exam). It is pronounced /ɡz/ when it also precedes a silent h and an accented vowel (e.g. exhaust).^[2] Before i or u, it can be pronounced /kʃ/ or /ɡʒ/ (e.g. sexual and luxury); these result from earlier /ksj/ and /ɡzj/. It also makes the sound /kʃ/ in words ending in -xion (typically used only in British-based spellings of the language; American spellings tend to use -ction). When x ends a word, it is always /ks/ (e.g. ax), except in loan words such as faux (see French, below).

There are very few English words that start with x (the least amount of any letter). When x does start a word, it is usually pronounced /z/ (e.g. xylophone, xenophobia, and xanthan); in rare recent loanwords or foreign proper names, it can also be pronounced /s/ (e.g. the obsolete Vietnamese monetary unit xu) or /ʃ/ (e.g. Chinese names starting with Xi like Xiaomi or Xinjiang). Many of the words that start with x are either 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). It does not begin any words in Basic English (but it occurs in words beginning with other letters).

It is the third least common letter in English (after Q and Z), with a frequency of about 0.15% in words.^[3]

Use in other languages

In the International Phonetic Alphabet, [x] represents a voiceless velar fricative.

In Latin, 'x' stood for [ks]. In some languages, as a result of assorted phonetic changes, handwriting adaptations or simply spelling convention, 'x' has other pronunciations:

Basque: as a spelling for [ʃ]. Additionally there is the digraph 'tx' [tʃ].
Dutch: X usually represents [ks], except in the name of the island of Texel, which is pronounced Tessel. This is because of historical sound-changes in Dutch, where all -x- sounds have been replaced with -s- sounds. Words with an -x- in the Dutch language are nowadays usually loanwords.
In Norwegian, 'x' is generally pronounced [ks], but since the 19th century, there has been a tendency to spell it out as 'ks'; 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, German and Finnish is similar.
French: at the ends of words, silent (or [z] in liaison if the next word starts with a vowel). Three exceptions are pronounced [s]: six ("six"), dix ("ten") and in some city names such as Bruxelles (although some people still pronounce it 'ks') or Auxerre. It is pronounced [z] in sixième and dixième.
In Italian, 'x' is either pronounced [ks], as in extra, uxorio, xilofono,^[4] or [ɡz], as exogamia, when it is preceded by 'e' and followed by a vowel. In several related languages, notably Venetian, it represents the voiced sibilant [z]. It is also used, mainly amongst the young people, as a short written form for "per", meaning "for": for example, "x sempre" ("forever"). This because in Italian the multiplication sign (similar to 'x') is called "per". However, 'x' is only found in loanwords, as it is not part of the standard Italian alphabet; in most words with 'x', 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).
Spanish: In Old Spanish, 'x' was pronounced [ʃ], as it is still currently in other Iberian Romance languages. Later, the sound evolved to a hard [x] sound. In modern Spanish, the [x] sound is generally spelled as the letters 'j' or 'g', though 'x' is still retained for some names (notably 'México', which alternates with 'Méjico'). Presently, 'x' represents the sound [s] (word-initially), or the consonant cluster [ks] (e.g. oxígeno, examen). Rarely, the 'x' can be pronounced [ʃ] as in Old Spanish in some proper nouns such as 'Raxel' (a variant of Rachel) and Uxmal.
In Galician (a language related to Portuguese and spoken in Northwestern Spain), and Leonese, used in Spain, 'x' is pronounced [ʃ] in most cases. In learned words, such as 'taxativo' (taxing), the 'x' is pronounced [ks]. However, Galician speakers tend to pronounce it [s], especially when it appears before plosives, such as in 'externo' (external).
In Catalan, 'x' has three sounds; the most common is [ʃ]; as in 'xarop' (syrup). Other sounds are: [ks]; 'fixar' (to fix), [ɡz]; 'examen'. In addition [ʃ] gets voiced to [ʒ] before voiced consonants; 'caixmir'. Catalan also has the digraph 'tx', pronounced [tʃ].
In Portuguese, 'x' has four main sounds; the most common is [ʃ], as in 'xícara' (cup). The other sounds are: [ks] as in 'fênix/fénix' (phoenix); [s], when preceded by E and followed by a consonant, as in 'contexto' ([ʃ] in European Portuguese), and in a small number of other words, such as 'próximo' (close/next); and (the rarest) [z], which occurs in the prefix 'ex' before a vowel, as in 'exagerado' (exaggerated). A rare fifth sound is [ɡz], coexisting with [z] and [ks] as acceptable pronunciations in exantema and in words with the Greek prefix 'hexa'.
In Venetian it represents the voiced alveolar sibilant [z] 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 [veˈnɛsja] in which 'x' has evolved from the initial voiced sibilant [z] to the present day voiceless sibilant.
In Albanian, 'x' represents [dz], while the digraph 'xh' represents [dʒ].
In Maltese, 'x' is pronounced [ʃ] or, in some cases, [ʒ] (only in loanwords such as 'televixin', and not for all speakers).

Additionally, in languages for which the Latin alphabet has been adapted only recently, 'x' 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 'x' can be written by other means, the letter becomes available for more unusual sounds.

X represents [x] in e.g. Azerbaijani, Kurdish, Lojban, Tatar, Uzbek, Pashto and Uyghur (Latin script).
Esperanto: The x-convention replaces ĉ, ĝ, ĥ, ĵ, ŝ, and ŭ with x-suffixes: cx, gx, hx, jx, sx, and ux.
In Indian languages, 'x' represents the consonant cluster [kʃ] in alternate spellings of words containing 'क्ष' (kṣ), especially names such as Laxmi and Dixit. Less frequently, 'x' is used to represent 'ख़' [x].
In Nahuatl, 'x' represents [ʃ].
Nguni languages: 'x' represents the alveolar lateral click [ǁ].
In Pirahã, 'x' symbolizes the glottal stop [ʔ].
An illustrating example of 'x' as a "leftover" letter is differing usage in three different Cushitic languages:
- Afar: voiced alveolar implosive [ɗ]
- Oromo: alveolar ejective [tʼ]
- Somali: voiceless pharyngeal fricative [ħ]

Usage in Southeast Asia and China

In Lao, based on romanization of Lao consonants, 'x' may represent [ɕ], e.g. in Lan Xang.
In Vietnamese, 'x' is pronounced like English s (at the beginning of a word, e.g. "sing"). This sound was [ɕ] in Middle Vietnamese, resembling the Portuguese sound /ʃ/, spelled 'x'.
In Hanyu Pinyin, Standard Chinese's official transcription system in China, Malaysia, Singapore, and Taiwan, the letter 'x' represents the voiceless alveolo-palatal fricative /ɕ/, for instance in 'Xi', [ɕi]. This sound somewhat resembles [ʃ].

Metalinguistic usage

In mathematics, 'x' is commonly used as the name for an independent variable or unknown value. The modern tradition of using 'x' to represent an unknown was started by René Descartes in La Géométrie (1637).^[5]

It may also be used to signify the multiplication operation when a more appropriate glyph is unavailable. 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.

Non-mathematical usage

Abbreviation for 'between' in the context of historical dating; e.g., '1483 x 1485.'
As a result of its use in algebra, X is often used to represent unknowns in other circumstances (e.g. Person X, Place X, etc.; see also Malcolm X).
In the Cartesian coordinate system x is used to refer to the horizontal axis.
X-rays are so called because their discoverer did not know what they were.
X has been used as a namesake for a generation of humans: Generation X, commonly abbreviated to Gen X. It is the generation born after the baby boom ended, ranging from 1961 to 1981.
An X-shaped mark has traditionally been used by the illiterate in lieu of a signature, and is also used to indicate a signature line on forms.
X marks are used to indicate the concept of negation or incorrect, the opposite of a Tick (check mark). They are also used as a substitute for the check mark (most notably on election Ballot papers)
X is commonly used as a generic mark (selecting an item on a form, indicating a location on a map, etc.).
The common custom of placing Xs on envelopes, notes and at the bottom of letters to mean kisses dates back to the Middle Ages, when a Christian cross was drawn on documents or letters to mean sincerity, faith, and honesty.
Usually in art or fashion, the use of X indicates a collaboration with two or more artists. The application extends to any other kinds of collaboration outside the art world. Originally started in Japan.
In cartoons, a dead character's eyes are often drawn as Xs.
In mapping by the standards of the USGS, an x-type mark is used to denote the point referred to by an elevation marking on topographical maps.
Maps leading to hidden treasure often denote the treasure with an X. The expression "X marks the spot" is related to these treasure maps.
X, and its Greek counterpart Chi, play roles in the Kingdom Hearts series. X is used in the names of the members of Organization XIII to change it around into an anagram. For example, Ansem with a X turns into Xemnas and Sora turns into Roxas, whereas Chi is used in the name of the ultimate weapon, the X-Blade, pronounced Chi-Blade. The series primary antagonist, Xehanort, whose name is also an anagram for No Heart or Another, even provides a quick explanation in the prequel Kingdom Hearts: Birth by Sleep.
The Man from Planet X, 1951 American science-fiction movie.
X: The Unknown, 1956 British science-fiction movie.
X: The Man with the X-ray Eyes, 1963 American science-fiction movie.
Malcolm X, 1992 American biopic of Malcolm X.
The X-Files, 1993-2002 American science-fiction television series.
"X", 2015 mystery novel by Sue Grafton

Computing codes

Character	X		x
Unicode name	LATIN CAPITAL LETTER X		LATIN SMALL LETTER X
Encodings	decimal	hex	decimal	hex
Unicode	88	U+0058	120	U+0078
UTF-8	88	58	120	78
Numeric character reference	X	X	x	x
EBCDIC family	231	E7	167	A7
ASCII ¹	88	58	120	78

¹ Also for encodings based on ASCII, including the DOS, Windows, ISO-8859 and Macintosh families of encodings.

In the C programming language, 'x' preceded by zero (0x or 0X) is used to denote hexadecimal literal values.

Related letters and other similar characters

Χ χ : Greek letter Chi
Ξ ξ : Greek letter Xi
א : Hebrew letter Aleph
Х х : Cyrillic letter Kha
ᚷ : Gyfu, a letter in the Anglo-Saxon futhorc runic alphabet used in pre-Norman Britain.
乂 : a Chinese character, pronounced [i] (high falling tone), "yì" in pinyin
ㄨ : a letter representing [u] or [w] in Mandarin Phonetic Symbols
メ : Me, a Japanese katakana character
× : Multiplication sign
Ⓧ : a symbol used in Japan for resale price maintenance

Other representations

NATO phonetic	Morse code
X-ray	–··–


Signal flag	Flag semaphore	Braille dots-1346

References

↑ "X", Oxford English Dictionary, 2nd edition (1989); Merriam-Webster's Third New International Dictionary of the English Language, Unabridged (1993); "ex", op. cit.
↑ Venezky, Richard (1 January 1970). The Structure of English Orthography. Walter de Gruyter. p. 40. ISBN 978-3-11-080447-8.
↑ Mička, Pavel. "Letter frequency (English)". Algoritmy.net. Retrieved 9 February 2014.
↑ "Dizionario di ortografia e pronunzia" [Dictionary of Spelling and preliminary]. Dizionario di ortografia e pronunzia (in Italian). Retrieved 9 February 2014.
↑ Cajori, Florian (1993). A History of Mathematical Notations. Google Books (Dover Publications).