Chi (letter)

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Chi (uppercase Χ, lowercase χ; Greek: χῖ) is the 22nd letter of the Greek alphabet, pronounced /ˈk/ or /ˈk/ in English.

Greek

The Greek alphabet on a black figure vessel, with a cross-shaped chi.

Pronunciation

Ancient Greek

Its value in Ancient Greek was an aspirated velar stop /kʰ/ (in the Western Greek alphabet: /ks/).

Koine Greek

In Koine Greek and later dialects it became a fricative ([x] / [ç]) along with Θ and Φ.

Modern Greek

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.

Transliteration

Chi is Romanized as ch in most systematic transliteration conventions, but sometimes kh is used.[1] In addition, in Modern Greek, it is often also Romanized as h or x in informal practice.

Greek numeral

In the system of Greek numerals, it has a value of 600.

Xi

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.

Cyrillic

Chi was also included in the Cyrillic script as the letter Х, with the phonetic value /x/ or /h/.

International Phonetic Alphabet

In the International Phonetic Alphabet, the minuscule chi is the symbol for the voiceless uvular fricative.

Chiasmus

Chi is the basis for the name Chiastic structure and the name of Chiasmus.

Symbolism

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.

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.

Character Encodings

  • Greek Chi
Character 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 decimal hex decimal hex decimal hex decimal hex
Unicode 935 U+03A7 967 U+03C7 7521 U+1D61 7530 U+1D6A 9767 U+2627
UTF-8 206 167 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 Greek-2 210 D2 243 F3
Windows 1253 214 D6 246 F6
TeX \chi

[2]

  • Coptic Khi
Character
Unicode name COPTIC CAPITAL LETTER KHI COPTIC SMALL LETTER KHI COPTIC SYMBOL KHI RHO
Encodings decimal hex decimal hex decimal hex
Unicode 11436 U+2CAC 11437 U+2CAD 11497 U+2CE9
UTF-8 226 178 172 E2 B2 AC 226 178 173 E2 B2 AD 226 179 169 E2 B3 A9
Numeric character reference Ⲭ Ⲭ ⲭ ⲭ ⳩ ⳩
  • Mathematical Chi
Character 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 decimal hex decimal hex decimal hex decimal hex decimal hex
Unicode 120510 U+1D6BE 120536 U+1D6D8 120568 U+1D6F8 120594 U+1D712 120626 U+1D732 120652 U+1D74C
UTF-8 240 157 154 190 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
UTF-16 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
Character 𝝬 𝞆 𝞦 𝟀
Unicode name MATHEMATICAL SANS-SERIF
BOLD CAPITAL CHI
MATHEMATICAL SANS-SERIF
BOLD SMALL CHI
MATHEMATICAL SANS-SERIF
BOLD ITALIC CAPITAL CHI
MATHEMATICAL SANS-SERIF
BOLD ITALIC SMALL CHI
Encodings decimal hex decimal hex decimal hex decimal hex
Unicode 120684 U+1D76C 120710 U+1D786 120742 U+1D7A6 120768 U+1D7C0
UTF-8 240 157 157 172 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
UTF-16 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.

Math and science

In statistics, the term chi-squared or χ² has various uses, including the chi-squared distribution, the chi-squared test, and chi-squared target models.

In algebraic topology, Chi is used to represent the Euler characteristic of a surface.

In neurology, the optic chiasm is named for the letter Chi because of its Χ-shape.[3]

In chemistry, the mole fraction[4][5] and electronegativity[6] may be denoted by the lowercase χ.

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 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.

See also

References

  1. ^ Encyclopedia Britannica
  2. ^ Unicode Code Charts: Greek and Coptic (Range: 0370-03FF)
  3. ^ Asimov, Isaac (1963). The Human Brain. Boston: Houghton Mifflin. 
  4. ^ Zumdahl, Steven S. (2008). Chemistry (8th ed.). Cengage Learning. p. 201. ISBN 0547125321. 
  5. ^ Rickard, James N. Spencer, George M. Bodner, Lyman H. (2010). Chemistry : structure and dynamics. (5th ed.). Hoboken, N.J.: Wiley. p. 357. ISBN 9780470587119. 
  6. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "Electronegativity".