Greek alphabet  



History  
Use in other languages  
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Chi /ˈkaɪ, ˈxiː/ (listen)^{[1]}^{[2]} (uppercase Χ, lowercase χ; Greek: χῖ) is the twentysecond letter of the Greek alphabet.
Its value in Ancient Greek was an aspirated velar stop /kʰ/ (in the Western Greek alphabet: /ks/).
In Koine Greek and later dialects it became a fricative ([x]/[ç]) along with Θ and Φ.
In Modern Greek, it has two distinct pronunciations: In front of high or front vowels (/e/ or /i/) it is pronounced as a voiceless palatal fricative [ç], as in German ich or like the h in some pronunciations of the English words hew and human. In front of low or back vowels (/a/, /o/ or /u/) and consonants, it is pronounced as a voiceless velar fricative ([x]), as in German ach or Spanish j.
Chi is romanized as ⟨ch⟩ in most systematic transliteration conventions, but sometimes ⟨kh⟩ is used.^{[3]} In addition, in Modern Greek, it is often also romanized as ⟨h⟩ or ⟨x⟩ in informal practice.
In the system of Greek numerals, it has a value of 600.
In ancient times, some local forms of the Greek alphabet used the chi instead of xi to represent the /ks/ sound. This was borrowed into the early Latin language, which led to the use of the letter X for the same sound in Latin, and many modern languages that use the Latin alphabet.
Chi was also included in the Cyrillic script as the letter Х, with the phonetic value /x/ or /h/.
Chi is the basis for the name literary chiastic structure and the name of chiasmus.
In Plato's Timaeus, it is explained that the two bands that form the soul of the world cross each other like the letter Χ. Plato's analogy, along with several other examples of chi as a symbol occur in Thomas Browne's discourse The Garden of Cyrus (1658).
Chi or X is often used to abbreviate the name Christ, as in the holiday Christmas (Xmas). When fused within a single typespace with the Greek letter rho, it is called the labarum and used to represent the person of Jesus Christ.
Preview  Χ  χ  ᵡ  ᵪ  ☧  

Unicode name  GREEK CAPITAL LETTER CHI  GREEK SMALL LETTER CHI  MODIFIER LETTER SMALL CHI  GREEK SUBSCRIPT SMALL LETTER CHI  CHI RHO  
Encodings  decimal  hex  dec  hex  dec  hex  dec  hex  dec  hex 
Unicode  935  U+03A7  967  U+03C7  7521  U+1D61  7530  U+1D6A  9767  U+2627 
UTF8  206 167  CE A7  207 135  CF 87  225 181 161  E1 B5 A1  225 181 170  E1 B5 AA  226 152 167  E2 98 A7 
Numeric character reference  Χ 
Χ 
χ 
χ 
ᵡ 
ᵡ 
ᵪ 
ᵪ 
☧ 
☧ 
Named character reference  Χ  χ  
DOS Greek  148  94  173  AD  
DOS Greek2  210  D2  243  F3  
Windows 1253  214  D6  246  F6  
TeX  \chi 
^{[4]}
Preview  Ⲭ  ⲭ  ⳩  

Unicode name  COPTIC CAPITAL LETTER KHI  COPTIC SMALL LETTER KHI  COPTIC SYMBOL KHI RHO  
Encodings  decimal  hex  dec  hex  dec  hex 
Unicode  11436  U+2CAC  11437  U+2CAD  11497  U+2CE9 
UTF8  226 178 172  E2 B2 AC  226 178 173  E2 B2 AD  226 179 169  E2 B3 A9 
Numeric character reference  Ⲭ 
Ⲭ 
ⲭ 
ⲭ 
⳩ 
⳩ 
Preview  Ꭓ  ꭓ  ꭔ  ꭕ  

Unicode name  LATIN CAPITAL LETTER CHI  LATIN SMALL LETTER CHI  LATIN SMALL LETTER CHI WITH LOW RIGHT RING  LATIN SMALL LETTER CHI WITH LOW LEFT SERIF  
Encodings  decimal  hex  dec  hex  dec  hex  dec  hex 
Unicode  42931  U+A7B3  43859  U+AB53  43860  U+AB54  43861  U+AB55 
UTF8  234 158 179  EA 9E B3  234 173 147  EA AD 93  234 173 148  EA AD 94  234 173 149  EA AD 95 
Numeric character reference  Ꭓ 
Ꭓ 
ꭓ 
ꭓ 
ꭔ 
ꭔ 
ꭕ 
ꭕ 
Preview  𝚾  𝛘  𝛸  𝜒  𝜲  𝝌  

Unicode name  MATHEMATICAL BOLD CAPITAL CHI 
MATHEMATICAL BOLD SMALL CHI 
MATHEMATICAL ITALIC CAPITAL CHI 
MATHEMATICAL ITALIC SMALL CHI 
MATHEMATICAL BOLD ITALIC CAPITAL CHI 
MATHEMATICAL BOLD ITALIC SMALL CHI  
Encodings  decimal  hex  dec  hex  dec  hex  dec  hex  dec  hex  dec  hex 
Unicode  120510  U+1D6BE  120536  U+1D6D8  120568  U+1D6F8  120594  U+1D712  120626  U+1D732  120652  U+1D74C 
UTF8  240 157 154 190  F0 9D 9A BE  240 157 155 152  F0 9D 9B 98  240 157 155 184  F0 9D 9B B8  240 157 156 146  F0 9D 9C 92  240 157 156 178  F0 9D 9C B2  240 157 157 140  F0 9D 9D 8C 
UTF16  55349 57022  D835 DEBE  55349 57048  D835 DED8  55349 57080  D835 DEF8  55349 57106  D835 DF12  55349 57138  D835 DF32  55349 57164  D835 DF4C 
Numeric character reference  𝚾 
𝚾 
𝛘 
𝛘 
𝛸 
𝛸 
𝜒 
𝜒 
𝜲 
𝜲 
𝝌 
𝝌 
Preview  𝝬  𝞆  𝞦  𝟀  

Unicode name  MATHEMATICAL SANSSERIF BOLD CAPITAL CHI 
MATHEMATICAL SANSSERIF BOLD SMALL CHI 
MATHEMATICAL SANSSERIF BOLD ITALIC CAPITAL CHI 
MATHEMATICAL SANSSERIF BOLD ITALIC SMALL CHI  
Encodings  decimal  hex  dec  hex  dec  hex  dec  hex 
Unicode  120684  U+1D76C  120710  U+1D786  120742  U+1D7A6  120768  U+1D7C0 
UTF8  240 157 157 172  F0 9D 9D AC  240 157 158 134  F0 9D 9E 86  240 157 158 166  F0 9D 9E A6  240 157 159 128  F0 9D 9F 80 
UTF16  55349 57196  D835 DF6C  55349 57222  D835 DF86  55349 57254  D835 DFA6  55349 57280  D835 DFC0 
Numeric character reference  𝝬 
𝝬 
𝞆 
𝞆 
𝞦 
𝞦 
𝟀 
𝟀 
These characters are used only as mathematical symbols. Stylized Greek text should be encoded using the normal Greek letters, with markup and formatting to indicate text style.
In statistics, the term chisquared or has various uses, including the chisquared distribution, the chisquared test, and chisquared target models.
In algebraic topology, Chi is used to represent the Euler characteristic of a surface.
In neuroanatomy, crossings of peripheral nerves (such as the optic chiasm) are named for the letter Chi because of its Χshape.^{[5]}
In chemistry, the mole fraction^{[6]}^{[7]} and electronegativity^{[8]} may be denoted by the lowercase .
In physics, denotes electric or magnetic susceptibility.
In rhetoric, both chiastic structure (a literary device) and the figure of speech Chiasmus derive from their names from the shape of the letter Chi.
In mechanical engineering, chi is used as a symbol for the reduction factor of relevant buckling loads in the EN 1993, a European Standard for the design of steel structures.
In graph theory, a lowercase chi is used to represent a graph's chromatic number.
In analytic number theory, chi is used for the Dirichlet character.