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X, or x, is the twenty-fourth and third-to-last letter in the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. 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''. X is regularly pronounced as "ks".

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

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'' (except for ''axion''). 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 'z' (e.g. ''xylophone'', ''xenophobia'', and ''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 (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-" (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 .
*french: at the ends of words, 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'' or ''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