X: Difference between revisions

{{Short description|24th letter of the Latin alphabet}}

{{About|the letter|other uses}}

{{Hatnote group|

}}

<br>[{{IPAlink|t͡ʃ}}]<br>[{{IPAlink|sʲ}}]<br>[{{IPAlink|z}}]<br>[{{IPAlink|g}}{{IPAlink|z}}]<br>{{IPAblink|∅}}<br>{{IPAc-en|ɛ|k|s}}

|fam1=[[wikt:𓊽|𓊽]]

|fam2=[[wikt:𐤎|𐤎]]

|fam3=[[wikt:𐤎|𐤎]]|fam4=[[Xi (letter)|𐊑]]|fam5=[[Chi (letter)|𐊐]]|fam6=[[𐌗|𐊐]]|image=File:Latin_letter_X.svg}}

'''X''', or '''x''', is the twenty-fourth [[Letter (alphabet)|letter]] of the [[Latin alphabet]], used in the [[English alphabet|modern English alphabet]], the alphabets of other western European languages and others worldwide. Its name in English is [[Wikt:ex#English|''ex'']] (pronounced {{IPAc-en|'|ɛ|k|s}}), plural ''exes''.<ref name=":1">"X", ''[[Oxford English Dictionary]]'', 2nd edition (1989); ''Merriam-Webster's Third New International Dictionary of the English Language, Unabridged'' (1993); "ex", ''op. cit''.</ref>

|-

! Western Greek<br />[[Chi (letter)|Chi]]

! Etruscan<br/>X

! Latin<br />X

|- style="background-color:white; text-align:center;"

| [[Image:Greek Chi normal.svg|45px]]

| [[File:Capitalis monumentalis X.SVG|x30px]]

The letter {{angbr|X}}, representing {{IPA|/ks/}}, was inherited from the [[Etruscan alphabet]]. It perhaps originated in the {{angbr|Χ}} of the [[Archaic Greek alphabets#Euboean|Euboean alphabet]] or another Western Greek alphabet, which also represented {{IPA|/ks/}}. Its relationship with the {{angbr|Χ}} of the Eastern Greek alphabets, which represented {{IPA|/kʰ/}}, is uncertain.

The pronunciation of {{IPA|/ks/}} in the [[Romance languages]] underwent [[Palatalization in the Romance languages|sound changes]], with various outcomes:

* [[French language|French]]: {{IPA|/js/}} (e.g. ''laisser'' from ''laxare'')

* [[Italian language|Italian]]: {{IPA|/ss/}} (e.g. ''asse'' from ''axem'') and, in some cases, {{IPA|/ʃʃ/}} (e.g. ''lasciare'' from ''laxare'')

* [[Portuguese language|Portuguese]]: {{IPA|/jʃ/}} (e.g. ''eixo'' from ''axem'')

* [[Romanian language|Romanian]]: {{IPA|/ps/}} (e.g. ''coapsă'' from ''coxa'') and {{IPA|/s/}} (e.g. ''lăsa'' from ''laxare'')

* [[Old Spanish]]: {{IPA|/ʃ/}}

** [[Spanish language|Spanish]]: {{IPA|/x/}} (e.g. ''cuja'' from ''coxa'')

In Old Spanish, {{angbr|x}} thus came to represent {{IPA|/ʃ/}}, which it still represents in most [[Iberian languages]] and in the orthographies of other languages influenced by Spanish, such as [[Nahuatl language|Nahuatl]]. In French (with a few exceptions), Italian, Romanian, and modern Spanish, {{angbr|x}} was replaced by other letters.

The use of {{angbr|x}} to represent {{IPA|/ks/}} was reintroduced to the Romance languages via Latin [[loanword]]s. In many words this {{IPA|/ks/}} was [[Consonant voicing and devoicing|voiced]] to {{IPA|/gz/}}.

== Use in writing systems ==

|+ Pronunciation of {{angbr|x}} by language

! Orthography

! Phonemes

! Environment

! [[Asturian orthography|Asturian]]

| {{IPAslink|ʃ}}, {{IPA|/ks/}}

|

|-

! [[Afar language|Afar]]

! [[Albanian orthography|Albanian]]

! [[Azerbaijani alphabet|Azeri]]

! [[Basque orthography|Basque]]

! rowspan="3" |[[Catalan orthography|Catalan]]

|{{IPAslink|ʃ}}

|Usually (word-initially, after consonants, ''i, au, eu'', in some surnames such as ''Rexach'')

|{{IPA|/gz/}}

|{{IPA|/ks/}}

! {{nwr|[[Standard Chinese]]}} ([[Pinyin]])

! [[Tsou language|Cou]]

|{{IPAslink|ɨ}} ~ {{IPAslink|ʉ}}

! rowspan="2" | [[Dutch orthography|Dutch]]

|{{IPA|/ks/}}

|Usually, mainly used in loanwords

! rowspan="4" | [[English orthography|English]]

|{{IPA|/ks/}}

|{{IPA|/gz/}}

|Before a stressed vowel

|{{IPAslink|h}}

|[[Don Quixote]], [[Oaxaca]], words derived from [[Classical Nahuatl]]/[[Nahuatl]]

|-

! [[Esperanto orthography|Esperanto]]

|''cx, gx, hx, jx, sx, ux'' are used as substitutes for ''ĉ, ĝ, ĥ, ĵ, ŝ, ŭ'' where these characters are not available, see [[X-convention]]

! rowspan="5" |[[French orthography|French]]

|{{IPA|/ks/}}

|{{IPA|/gz/}}

|Mainly in the [[prefix]] ex- followed by a vowel; sometimes word-initially

|Silent

|{{IPAslink|s}}

|In ''six'' ([[6]]), ''dix'' ([[10]]), ''[[Auxerre]]'', and ''Bruxelles'' ([[Brussels]])

! rowspan="2" |[[Galician alphabet|Galician]]

|{{IPA|/(k)s/}}

|Some learned loanwords

! [[German orthography|German]]

|{{IPA|/ks/}}

|Mainly used in loanwords

! rowspan="2" |[[Indonesian orthography|Indonesian]]

|{{IPAslink|s}}

|In the beginning of a word, mainly used in [[Loanword|loanwords]] for science

|{{IPA|/ks/}}

|In the middle or the end of a word, although words borrowed with the letter x in the middle or the end of a word are always replaced by the letters 'ks'. For example, the word 'maximum' and 'climax' in Indonesian would be 'maksimal' and 'klimaks'. Letter x on the middle or the end of a word only occurs in names. Mainly used in [[Loanword|loanwords]] for science.

! [[Italian orthography|Italian]]

|{{IPA|/ks/}}

|Mainly used in learned loanwords

|-

! [[Kurdish orthography|Kurdish]]

|{{IPAslink|x}}

! [[Lao language|Lao]] romanization

! [[Leonese dialect|Leonese]]

! [[Ligurian language|Ligurian]]

! [[Maltese orthography|Maltese]]

! [[Mayan languages|Mayan]] ([[Academia de Lenguas Mayas de Guatemala|ALMG]])

! [[Nahuatl orthography|Nahuatl]]

! [[Nguni language|Nguni]]

! [[Norwegian orthography|Norwegian]]

|{{IPA|/ks/}}

! rowspan="4" | [[Occitan orthography|Occitan]]

|{{IPAslink|s}}

|{{IPA|/ɡz/}}

|In the prefix ex- before vowels in the [[Provençal dialect|Provençal]], [[Limousin dialect|Limousin]], [[Auvergnat]], [[Vivaro-Alpine]], and [[Niçard]] dialects

|{{IPA|/ɡʒ/}}

|Before {{angbr|i}} and {{angbr|u}} in the [[Auvergnat]] dialect

! [[Oromo language|Oromo]]

! [[Pirahã language|Pirahã]]

! [[Polish orthography|Polish]]

|{{IPA|/ks ~ gz/}}

! rowspan="5" | [[Portuguese orthography|Portuguese]]

|{{IPAslink|ʃ}}

|Usually, especially word-initially; in words derived from [[Tupi language|Tupi]]

|{{IPA|/ks/}}

|Some words, mainly in learned loanwords

|When preceded by {{angbr|e}} and a consonant; some words

|{{IPA|/gz/}}

|In the [[prefix]] ''[[hexa-]]'' ("[[Numeral prefix|hexa]]-")

|-

! [[Sardinian alphabet|Sardinian]]

! rowspan="2" |[[Sicilian orthography|Sicilian]]

|{{IPAslink|ʃ}}

|Old Sicilian words and names, e.g. [[Bettino Craxi|Craxi]], [[Joppolo Giancaxio|Giancaxio]]

|{{IPA|/k(ə)s(ə)/}}

|Loanwords

! [[Somali orthography|Somali]]

|{{IPAslink|ħ}}

! rowspan="3" | [[Spanish orthography|Spanish]]

|{{IPA|/(k)s/}}

|{{IPAslink|ʃ}}, {{IPAslink|t͡ʃ}},{{IPAslink|x}}

|In some names and words

! [[Swedish orthography|Swedish]]

|{{IPA|/ks/}}

! [[Uzbek alphabet|Uzbek]]

! rowspan="2" | [[Venetian orthography|Venetian]]

|In ''Venexia'' "[[Venice]]"

|-

! [[Vietnamese orthography|Vietnamese]]

|{{IPAslink|s}}

In [[English orthography]], {{angbr|x}} is typically pronounced as the voiceless [[consonant cluster]] {{IPAc-en|k|s}} when it follows the stressed vowel (e.g. ''ox''), and the voiced consonant {{IPAc-en|ɡ|z}} when it precedes the stressed vowel (e.g. ''exam''). It is also pronounced {{IPAc-en|ɡ|z}} when it precedes a silent {{angbr|h}} and a stressed vowel (e.g. ''exhaust'').<ref name="Venezky1970">{{cite book|first=Richard|last=Venezky|title=The Structure of English Orthography|url=https://books.google.com/books?id=Mrt_G_RrJykC&pg=PA5|date=1 January 1970|location=[[The Hague]]|publisher=Walter de Gruyter|isbn=978-3-11-080447-8|page=40|access-date=29 October 2016|archive-date=27 April 2017|archive-url=https://web.archive.org/web/20170427105102/https://books.google.com/books?id=Mrt_G_RrJykC&pg=PA5|url-status=live}}</ref>

Due to [[yod-coalescence]], the sequence {{angbr|xi}} before a vowel can be pronounced {{IPAc-en|k|ʃ}} resulting from earlier {{IPAc-en|k|s|j}}, e.g. in ''-xion(-)'', ''-xious(-)''. Similarly, the sequence {{angbr|xu}} can be pronounced with {{IPAc-en|k|ʃ}} (e.g. ''flexure'', ''sexual'') or {{IPAc-en|ɡ|ʒ}} (in ''luxury'' and its derivatives)<!-- Oxford gives /ˈlʌkʃ(ə)ri/-->

Due to [[NG-coalescence]], the sequence {{angbr|nx}} can be pronounced {{IPAc-en|ŋ|z}} in ''anxiety''.

When {{angbr|x}} ends a word, it is always {{IPAc-en|k|s}} (e.g. ''fax''), except in loan words such as ''faux'' (see French, below).

There are very few English words that start with {{angbr|x}} (the fewest of any letter). When {{angbr|x}} does start a word, it is usually pronounced 'z' (e.g. ''xylophone'', ''xanthan''). When starting in some names or as its own representation it is pronounced 'eks', in rare recent loanwords or foreign proper names, it can also be pronounced {{IPAc-en|s}} (e.g. the obsolete Vietnamese monetary unit ''[[wiktionary:xu|xu]]'') or {{IPAc-en|ʃ}} (e.g. Chinese names starting with Xi like [[Xiaomi]] or [[Xinjiang]]). Many of the words that start with {{angbr|x}} are of [[Greek language|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-" (e.g. ''Xmas'' for Christmas, ''Xian'' for Christian), the "crys-" in crystal (''XTAL''), "by" (''SXSW'' for [[South by Southwest]]) or various words starting with "ex-" (e.g. ''XL'' for extra large, ''XOR'' for [[Exclusive disjunction|exclusive-or]], or the [[extinction symbol]]).

===Romance languages===

In Latin, {{angbr|x}} stood for {{IPA|/ks/}}. In the [[Romance languages]], as a result of assorted phonetic changes, {{angbr|x}} has other pronunciations:

*In [[Catalan language|Catalan]], {{angbr|x}} has three pronunciations; the most common is {{IPAslink|ʃ}}; as in 'xarop' (syrup). Others are: {{IPA|/ks/}}; 'fixar' (to fix), {{IPA|/ɡz/}}; 'examen'. In addition, {{IPAslink|ʃ}} gets voiced to {{IPAblink|ʒ}} before voiced consonants; 'caixmir'. Catalan also has the digraph {{angbr|tx}}, pronounced {{IPAslink|tʃ}}.

*In [[Galician language|Galician]] and [[Leonese language|Leonese]], {{angbr|x}} is pronounced {{IPAslink|ʃ}} in most cases (often used in place of etymological ''g'' or ''j''). The pronunciation {{IPA|/ks/}} occurs in learned words, such as '<nowiki/>''taxativo''<nowiki/>' (taxing). However, Galician speakers tend to pronounce it {{IPAslink|s}}, especially when it appears before plosives, such as in '''externo''<nowiki/>' (external).

*In [[French language|French]], {{angbr|x}} usually represents {{IPA|/ks/}} or (primarily in words beginning with ex- followed by a vowel) {{IPA|/ɡz/}}. It is pronounced {{IPAslink|s}} in some city names such as ''[[Brussels|Bruxelles]]'' (although some people pronounce it 'ks') or ''[[Auxerre]]''; it is nevertheless pronounced {{IPA|/ks/}} in [[Aix (disambiguation)|Aix]], the name of several towns. At the ends of other words, it is silent (or {{IPAslink|z}} in [[Liaison (French)|liaison]] if the next word starts with a vowel). Two exceptions are pronounced {{IPAslink|s}}: ''six'' ("six"), ''dix'' ("ten"). It is pronounced {{IPAslink|z}} in ''sixième'' and ''dixième''.

*In [[Italian language|Italian]], {{angbr|x}} is either pronounced {{IPA|/ks/}}, as in ''extra'', ''uxorio'', ''xilofono'',<ref>{{cite web |url=http://www.dizionario.rai.it |title=Dizionario di ortografia e pronunzia |trans-title=Dictionary of Spelling and Pronunciation |language=it |website=Dizionario di ortografia e pronunzia |access-date=9 February 2014 |archive-date=16 April 2018 |archive-url=https://web.archive.org/web/20180416110248/http://www.dizionario.rai.it/ |url-status=live }}</ref> or {{IPA|/ɡz/}}, as ''exogamia'', when it is preceded by {{angbr|e}} and followed by a vowel. In several related languages, notably Venetian, it represents the voiced sibilant {{IPAslink|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 is because in Italian the [[×|multiplication sign]] (similar to {{angbr|x}}) is called "per". However, {{angbr|x}} is found only in [[loanword]]s, as it is not part of the standard [[Italian alphabet]]; in most words with {{angbr|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/[[:it:clacson|clacson]]'').

*In [[Portuguese language|Portuguese]], {{angbr|x}} has four main pronunciations; the most common is {{IPAslink|ʃ}}, as in 'xícara' (cup). The other sounds are: {{IPA|/ks/}} as in 'flexão' (flexion); {{IPAslink|s}}, when preceded by E and followed by a consonant, as in 'contexto' ({{IPAslink|ʃ}} in European Portuguese), and in a small number of other words, such as 'próximo' (close/next); and (the rarest) {{IPAslink|z}}, which occurs in the prefix 'ex-' before a vowel, as in 'exagerado' (exaggerated). A rare fifth sound is {{IPA|/ɡz/}}, coexisting with {{IPAslink|z}} and {{IPA|/ks/}} as acceptable pronunciations in ''exantema'' and in words with the Greek prefix 'hexa-'.

*In [[Sardinian language|Sardinian]] and [[Ligurian (Romance language)|Ligurian]], {{angbr|x}} represents {{IPAslink|ʒ}}.

*In [[Old Spanish]], {{angbr|x}} was pronounced {{IPAslink|ʃ}}, as it is still currently in other [[Iberian Romance languages]]. Later, the sound evolved to a {{IPAslink|x}} sound. In modern [[Spanish language|Spanish]], due to a spelling reform, whenever {{angbr|x}} is used for the {{IPAslink|x}} sound it has been replaced with {{angbr|j}}, including in words that originally had {{angbr|x}} such as ''ejemplo'' or ''ejercicio'', though {{angbr|x}} is still retained for some names (notably 'México', even though 'Méjico' may sometimes be used in Spain). Presently, {{angbr|x}} represents the sound {{IPAslink|s}} (word-initially), or the consonant cluster {{IPA|/ks/}} (e.g. ''oxígeno, examen''). Rarely, it can be pronounced {{IPAslink|ʃ}} as in Old Spanish in some proper nouns such as 'Raxel' (a variant of [[Rachel]]) and ''[[Uxmal]]''.

*In [[Venetian language|Venetian]], {{angbr|x}} represents the voiced alveolar sibilant {{IPAslink|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'' or ''caxa'' (home). Nowadays, the best-known word is ''xe'' (is/are). The most notable exception to this rule is the name ''Venexia'' {{IPA|/veˈnɛsja/}} in which {{angbr|x}} has evolved from the initial voiced sibilant {{IPAslink|z}} to the present day voiceless sibilant {{IPAslink|s}}.

In languages which adopted the [[Latin script|Latin alphabet]] later, {{angbr|x}} is used for various sounds, in some cases inspired by Latin or its descendants, but in others for unrelated consonants. Since the various Romance pronunciations of {{angbr|x}} can often be written in other ways, the letter becomes available for other sounds.

*In [[Albanian language|Albanian]], {{angbr|x}} represents {{IPAslink|dz}} while the [[Digraph (orthography)|digraph]] {{angbr|xh}} represents {{IPAslink|dʒ}}.

*It represents {{IPAslink|x}} ([[voiceless velar fricative]]) in [[Apache]], [[Azerbaijani language|Azerbaijani]], [[Kurdish language|Kurdish]] (Hawar alphabet), [[Georgian language|Georgian]] (when Latinized), [[Lojban]], [[Pashto]] (when Latinized), [[Tatar language|Tatar]] (Jaꞑalif, Zamanälif, official romanization of 2012), [[Uzbek language|Uzbek]], and [[Uyghur language|Uyghur]] ([[Uyghur Latin alphabet|Latin script]]).

*In [[Basque language|Basque]], {{angbr|x}} represents {{IPAslink|ʃ}}. Additionally, the digraph {{angbr|tx}} represents {{IPAslink|tʃ}}.

*In [[Hanyu Pinyin]], [[Standard Chinese]]'s official transcription system in China, Malaysia, Singapore, and Taiwan, the letter {{angbr|x}} represents the [[voiceless alveolo-palatal fricative]] {{IPAslink|ɕ}}, for instance in '[[Xi (surname)|Xi]]', {{IPA|/ɕi/}}.

*In [[Dutch language|Dutch]], {{angbr|x}} usually represents {{IPA|/ks/}}, except in the name of the island of [[Texel]], which is pronounced ''Tessel''. This is because of [[Dutch language#Historical sound changes|historical sound-changes in Dutch]], where all {{IPA|/ks/}} sounds have been replaced by {{IPAslink|s}} sounds. Words with an {{angbr|x}} in the Dutch language are nowadays usually [[loanword]]s. In the [[Languages of Belgium|Dutch-speaking part of Belgium]], [[family name]]s with {{angbr|x}} are not uncommon (e.g. Dierckx, Hendrickx, Koninckx, Sterckx, Vranckx).

*In [[Esperanto]], the [[x-convention]] replaces {{angbr|[[ĉ]]}}, {{angbr|[[ĝ]]}}, {{angbr|[[ĥ]]}}, {{angbr|[[ĵ]]}}, {{angbr|[[ŝ]]}}, and {{angbr|[[ŭ]]}} with x-suffixes: {{angbr|cx}}, {{angbr|gx}}, {{angbr|hx}}, {{angbr|jx}}, {{angbr|sx}}, and {{angbr|ux}}.

*In [[German language|German]], generally pronounced {{IPA|/ks/}}; in native words, however, such as ''Ochs'' or ''wachsen'', the cluster {{IPA|/ks/}} is often written {{angbr|chs}}.

*In transliterations of [[Languages of India|Indian languages]], primarily Indo-Aryan languages, {{angbr|x}} represents the consonant cluster {{IPA|[kʃ]}} in alternate spellings of words containing 'क्ष' (kṣ), especially names such as [[Laxmi]] and [[Dikshit|Dixit]]. Less frequently, {{angbr|x}} is used to represent 'ख़' {{IPAslink|x}}.

*In [[Lao language|Lao]], based on [[romanization of Lao#Consonants|romanization of Lao consonants]], {{angbr|x}} may represent {{IPAslink|ɕ}}, e.g. in [[Lan Xang]].

*In [[Maltese language|Maltese]], {{angbr|x}} is pronounced {{IPAslink|ʃ}} or, in some cases, {{IPAslink|ʒ}} (only in loanwords such as 'televixin', and not for all speakers).

*In [[Nahuatl]], {{angbr|x}} represents {{IPAslink|ʃ}}.

*In [[Nguni languages]], {{angbr|x}} represents the [[alveolar lateral click]] {{IPAslink|ǁ}}.

*In [[Norwegian language|Norwegian]], {{angbr|x}} is generally pronounced {{IPA|/ks/}}, but since the 19th century, there has been a tendency to spell it out as {{angbr|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 language|Danish]] and [[Finnish language|Finnish]] is similar (while [[Swedish language|Swedish]], on the other hand, makes frequent use of {{angbr|x}} in native words as well as in loanwords).

*In [[Pirahã language|Pirahã]], {{angbr|x}} symbolizes the [[glottal stop]] {{IPAslink|ʔ}}.

*In [[Polish language|Polish]], {{angbr|x}} was used prior to 19th century both in loanwords and native words and was pronounced {{IPA|/ks/}} or {{IPA|/ɡz/}}, e.g. ''xiążę'', ''xięstwo'' (now ''książę'', ''księstwo''). This was later replaced by {{angbr|ks}} and {{angbr|gz}} 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.

*In [[Vietnamese alphabet#Consonants|Vietnamese]], {{angbr|x}} represents {{IPAslink|s}}. This sound was {{IPAblink|ɕ}} in Middle Vietnamese, resembling the Portuguese {{IPAslink|ʃ}}, spelled {{angbr|x}}.

An illustrating example of {{angbr|x}} as a "leftover" letter is differing usage in three different [[Cushitic languages]]:

*[[Afar language|Afar]]: [[voiced alveolar implosive]] {{IPAslink|ɗ}}

*[[Oromo language|Oromo]]: [[alveolar ejective]] {{IPAslink|tʼ}}

*[[Somali language|Somali]]: [[voiceless pharyngeal fricative]] {{IPAslink|ħ}}

{{main article|X (disambiguation)}}

* The [[Roman numeral]] X represents the number [[10 (number)|10]].<ref>{{cite book |last=Gordon |first=Arthur E. | url=https://archive.org/details/illustratedintro0000gord |url-access=registration |quote=roman numerals. | title=Illustrated Introduction to Latin Epigraphy | publisher=University of California Press | date=1983 | access-date=3 October 2015 | page=[https://archive.org/details/illustratedintro0000gord/page/44 44]|isbn=9780520038981 }}</ref><ref>{{cite book | last=King | first=David A. | url=https://books.google.com/books?id=PapljPXaSbwC&q=roman%20numerals%20letters&pg=PA282 | title=The Ciphers of the Monks | year=2001 | page=282 | publisher=Franz Steiner Verlag | isbn=9783515076401 | quote=In the course of time, '''I''', '''V''' and '''X''' became identical with three letters of the alphabet; originally, however, they bore no relation to these letters. | access-date=2020-11-22 | archive-date=2021-01-04 | archive-url=https://web.archive.org/web/20210104092429/https://books.google.com/books?id=PapljPXaSbwC&q=roman%20numerals%20letters&pg=PA282 | url-status=live }}</ref>

* 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 (mathematics)|unknown (''incognita'')]] was introduced by [[René Descartes]] in ''[[La Géométrie]]'' (1637).<ref>{{cite book |url=https://books.google.com/books?id=_byqAAAAQBAJ&q=unknown&pg=PA380 |title=A History of Mathematical Notations |first=Florian |last=Cajori |publisher=Open Court Publishing |year=1928 |place=Chicago |page=381 |isbn=9780486161167 |access-date=2020-11-22 |archive-date=2021-04-13 |archive-url=https://web.archive.org/web/20210413173747/https://books.google.com/books?id=_byqAAAAQBAJ&q=unknown&pg=PA380 |url-status=live }} See [[History of algebra#The symbol x|History of algebra]].</ref> 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.<ref name="Science as Culture">{{cite journal | first = Ingrid | last = Holme | title = Hearing People's Own Stories | journal = Science as Culture | volume = 17 | issue = 3 |pages = 341–344| doi = 10.1080/09505430802280784 | date = 2008 | s2cid = 143528047 }}</ref><ref name="nzpass">{{cite web|url=http://www.passports.govt.nz/Transgender-applicants|title=New Zealand Passports - Information about Changing Sex / Gender Identity|access-date=6 October 2014|url-status = live|archive-url=https://web.archive.org/web/20140923055123/http://www.passports.govt.nz/Transgender-applicants|archive-date=23 September 2014}}</ref>

* 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]], {{char|×}}. In mathematical typesetting, ''x'' meaning an algebraic variable is normally in [[italic type]] (<math>x\!</math>), 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".<ref>{{cite web | url=http://www.dictionary.com/browse/x-marks-the-spot | title=X marks the spot | access-date=21 June 2016 | archive-date=4 June 2016 | archive-url=https://web.archive.org/web/20160604015834/http://www.dictionary.com/browse/x-marks-the-spot | url-status=live }}</ref>

* 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.<ref>{{cite web|url=http://arkitip.com/product/x-mark-of-collaboration-issue-no-0053x/|title=X: Mark of Collaboration - Issue No. 0053X - Arkitip, Inc.|website=arkitip.com|access-date=2016-03-22|archive-date=2016-05-17|archive-url=https://web.archive.org/web/20160517184918/http://arkitip.com/product/x-mark-of-collaboration-issue-no-0053x/|url-status=live}}</ref> This usage mimics the use of a similar mark in [[Hybrid name (botany)|denoting botanical hybrids]], for which scientifically the [[Multiplication sign#Uses|multiplication ×]] is used, but informally a lowercase "x" is also used.

* {{Anchor|Kiss}}At the end of a letter or other correspondence, '[[Hugs and kisses|x]]' can mean a kiss;<ref>{{Cite news|last=Epstein|first=Nadine|date=2020-10-07|title=A whole lot of history behind 'x' and 'o', kiss and hug|url=https://www.washingtonpost.com/lifestyle/style/a-whole-lot-of-history-behind-x-and-o-kiss-and-hug/2014/02/13/0c3e218a-9341-11e3-b46a-5a3d0d2130da_story.html|url-status=live|access-date=2021-03-12|newspaper=[[The Washington Post]]|archive-date=2018-04-01|archive-url=https://web.archive.org/web/20180401143406/https://www.washingtonpost.com/lifestyle/style/a-whole-lot-of-history-behind-x-and-o-kiss-and-hug/2014/02/13/0c3e218a-9341-11e3-b46a-5a3d0d2130da_story.html}}</ref> the earliest example of this usage cited by the ''Oxford English Dictionary'' is from 1878.<ref>"[https://www.oed.com/view/Entry/230945 X, n.]" ''OED Online'' (Oxford: Oxford University Press, September 2022), §6. Accessed 11 November 2022.</ref>

* An [[X rating]] denotes media such as movies that are intended for adults only.

* In the [[Korean language]], a series of Xs is used as a visual [[bleep censor]] for subtitles and captions, serving the same role as an [[asterisk]] (*).<ref>{{Cite web |title='찐따', 'X랄하다'...욕도 전통을 가진다? |url=https://www.goeonair.com/news/article.html?no=13845 |access-date=2023-08-22 |website=www.goeonair.com |language=ko}}</ref><ref>{{Cite book |last=참바다 |url=https://books.google.com/books?id=XX4WEAAAQBAJ&dq=%EC%9A%95+X&pg=PA6-IA1 |title=시사칼럼 우리 시대의 상징과 은유 |date=2021-01-15 |publisher=e퍼플 |isbn=979-11-6569-712-9 |language=ko}}</ref>

* 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.<ref name=":1" />

**Ꭓ ꭓ : [[Latin chi]]

==Other representations==

===Computing <span class="anchor" id="Computing codes"></span>===

| 0058 | 0078 | FF38 | FF58 | name1 = Latin Capital Letter X | name2 = Latin Small Letter X | name3 = FULLWIDTH LATIN CAPITAL LETTER X | name4 = FULLWIDTH LATIN SMALL LETTERX

===Other===

{{Use dmy dates|date=June 2024}}