Chi (letter)

Chi uc lc.svg
Greek alphabet
Αα Alpha Νν Nu
Ββ Beta Ξξ Xi
Γγ Gamma Οο Omicron
Δδ Delta Ππ Pi
Εε Epsilon Ρρ Rho
Ζζ Zeta Σσς Sigma
Ηη Eta Ττ Tau
Θθ Theta Υυ Upsilon
Ιι Iota Φφ Phi
Κκ Kappa Χχ Chi
Λλ Lambda Ψψ Psi
Μμ Mu Ωω Omega
Other characters
Digamma uc lc.svg Digamma Greek Stigma.svg Stigma
Greek Heta.svg Heta Greek San.svg San
Qoppa Q-and-Z-shaped.svg Qoppa Greek Sampi 2 shapes.svg Sampi
Greek diacritics

Chi (uppercase Χ, lowercase χ; Greek: χῖ) is the 22nd letter of the Greek alphabet, pronounced as /ˈkaɪ/ in English. 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 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. Chi is Romanized as <ch> in most systematic transliteration conventions, but also sometimes as <h> or <x> in informal practice.

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

In ancient times, some dialects of Greek used the chi instead of xi to represent the /ks/ sound. This was borrowed into the early Latin language, which led to the letter X being used for the same sound in Latin, and the modern languages which use the Latin alphabet.

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

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

In Plato's Timaeus, it is explained that the two bands which 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.

The optic chiasm, an x-shaped connection of the optic nerves leading to the eye, got its name from the letter chi because of its shape;[1] likewise, the shape of the letter chi is the origin of the rhetorical device chiasmus.

In linguistics, chi is the symbol for a voiceless uvular fricative.

Chi is also frequently used in statistics.

In Algebraic Topology, Chi is used to represent the Euler Characteristic of a surface.

References

  1. ↑ Asimov, Isaac (1963). The Human Brain. Boston: Houghton Mifflin. 

See also