X, x （英文：aks；中文音译：亞克斯）是拉丁字母中的第24个字母。在北约音标字母中使用X-Ray来表示X。
/ks/音在古代的西部希腊语中用“Χ”（Chi）字母来表示；而在古代的东部希腊语中用“Ξ”（Xi）字母来表示，“Χ”（Chi）字母只表示/x/。
结果，现代希腊语采用了东方式的写法，但西方式的写法却传入了意大利半岛的伊特鲁里亚。因此它在伊特鲁里亚语中表示/ks/，在拉丁语中表示/ks/和/gs/；相反的，源自东希腊语的斯拉夫字母却继承了东希腊语的读法，以致现时东方的阿塞拜疆语，乌兹别克语、鞑靼语、维吾尔语都把X来标记/x/音。不过，有学者表明拉丁字母的X并不等同于希腊字母Χ。葡萄牙语中x表示[ʃ]。
但是对于字母Ψ (Psi)，Χ (Chi, Khi) 和 Ξ (Xi) 是来源于希腊语还是闪族语则仍有争论。
字母X的含意
大寫X代表
小写x代表
- 在代数学中，通常使用变量x来表示未知量；这个用法可以追索到阿拉伯语中。
- 在解析几何中通常用来表示水平的坐标轴。
其他用法
字符编码
参看
X (named ex /ˈɛks/, plural exes) is the twenty-fourth letter in the ISO basic Latin alphabet.
Uses
In mathematics, x is commonly used as the name for an independent variable or unknown value. The usage of x to represent an independent or unknown variable can be traced back to the Arabic word šay' شيء = “thing,” used in Arabic algebra texts such as the Al-Jabr. It was subsequently taken into Old Spanish with the pronunciation /ʃei/, which was written xei and soon habitually abbreviated to 
. (The Spanish pronunciation of ⟨x⟩ has changed since.) This started the habit of using letters to represent quantities in algebra.[citation needed]
It may also be used to signify the multiplication operation when a more appropriate glyph is unavailable. In mathematics, an "italicized x" (
) is often used to avoid potential confusion with the multiplication symbol. Another usage of X in mathematics is 
which is used to represent the cross product.
Other non-mathematical uses include:
- As a result of its use in math, X is often used to represent unknowns in other circumstances (e.g. Person X, Place X, etc.; see also Malcolm X).
- 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.
- X is also used for referring to 'the end of conversation'.
- X is used by the illiterate in lieu of a signature and indicates a signature line on forms.
- In cartoons, Xs are drawn instead of eyes to indicate the death of a character.
- X is commonly used as a generic mark (selecting an item on a form, indicating a location on a map, etc.).
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.) There has been much mostly fruitless debate about the origins of these added letters.
| Greek Xi
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Etruscan X |
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Usage
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 when it's used for the island of Texel, which is pronounced Tessel. This is because of a 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.
- English: X is typically a sign for the compound consonants [ks]; or sometimes when followed by an accented syllable beginning with a vowel, or when followed by silent h and an accented vowel [ɡz] (e.g. exhaust, exam); usually [z] at the beginnings of words (e.g. xylophone, Xenon), and in some compounds keeps the [z] sound, as in (e.g. meta-xylene). 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). Before i or u it can also represent the sounds [ɡʒ] or [kʃ], for example, in the words luxury and sexual, respectively: these result from earlier [ɡzj] and [ksj]. Final x is always [ks] (e.g. ax/axe) except in loan words such as faux (see French, below).
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 short hand 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).
There are very few English words that start with X – the least amount of any letter. Many of the words that do start with X are either standardized trademarks (XEROX) or acronyms (XC). 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. X is the third most rarely used letter in the English language.[citation needed]
-
French: at the ends of words, silent (or [z] in liaison if the next word starts with a vowel). This usage arose as a handwriting alteration of final -us. Three exceptions are pronounced [s]: six ("six"), dix ("ten") and Bruxelles ("Brussels"). It is pronounced [z] in sixième and dixième.
- In Italian, X is either pronounced [ks], as in extra, when it is followed by a consonant, or [ɡz], as in the words uxorio and xilofono, when it is followed by a vowel. In several northern regional languages, notably Venetian, it represents the voiced sibilant [z]. It is also used, mainly amongst the young, 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 that have become of common use, it has been replaced by the CS sequence.
- In Norwegian, X is generally pronounced [ks], 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. Usage in Swedish, Danish, German and Finnish is similar.
-
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 hard [x] 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 [s] (word-initially), or the consonant cluster [ks] (e.g. oxígeno, examen). Even more 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 in implosive position, 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 sounds; the most common is [ʃ], as in 'xícara' (cup). The other sounds are: [ks] as in 'fênix/fénix' (phoenix), [s], as in 'próximo' (close/next), and (the rarest) [z], as in 'exagerado' (exaggerate).
- 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 Uyghur (Latin script), x represents the sound [χ].
- 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 cx, gx, hx, jx, sx, and ux.
- In Hindi, x represents the sound [kʃ] in alternate spellings of words containing क्ष, especially names such as Laxmi or Madhuri Dixit.
- 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 East Cushitic languages:
In Southeast Asia and China
- 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 romanization of Lao consonants, X may represent the same sound, e.g. in Lan Xang, where the parallel Thai alphabetic character for the same word is pronounced chang.
- In Hanyu Pinyin, Mandarin 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].
Related letters and other similar characters
Computing codes
| character |
X |
x |
| Unicode name |
LATIN CAPITAL LETTER X |
LATIN SMALL LETTER X
|
| character encoding |
decimal |
hex |
decimal |
hex |
| Unicode |
88 |
0058 |
120 |
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 and all 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.
Other representations
See also
-
Media related to X at Wikimedia Commons
-
The Wiktionary entry for X
-
The Wiktionary entry for x
维基词典的解释：X, x
维基共享上的资源
. (The 
) is often used to avoid potential confusion with the multiplication symbol. Another usage of X in mathematics is 
which is used to represent the 
Media related to 
The Wiktionary entry for 
