Chi (letter)

Encyclopedia : C : CH : CHI : Chi (letter)

For other uses, see Chi.

Chi (upper case Χ, lower case χ) is the 22nd letter of the Greek alphabet. Its value in Ancient Greek was an aspirated velar stop (/k^h/), but in Koine and later dialects it fricativized along with Θ and Φ. In Modern pronunciation, it is a voiceless dorsal fricative. In front of "light" vowels (e, i, oi, ai, y) it is prounounced like the German ich-laut (/ç/) or some variants of 'h' in the English 'hew' or 'human'. In front of "dark" vowels (a, o, ou) and consonants, it is pronounced like the German ach-laut (/χ/) or in Scottish 'loch'.

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.

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

The upper-case letter Χ is used as the symbol for:

Part of or a subsitution for the Labarum monogram.
The name of Jesus Christ in Christianity, as in X-mas etc.
The last letter of the name of the TeX typesetting system.

The lower-case letter χ is used as the symbol for:

The chi-square distribution or Chi-square test in statistics.
The electric susceptibility (sometimes with a subscript e) and magnetic susceptibility in physics.
The chromatic number and the chromatic index (when shown with a prime mark or a subscript 1) of a graph in graph theory.
The Euler characteristic in algebraic topology.
The voiceless uvular fricative (IPA) in phonology.
An unsigned gathering in formal bibliographic collation.
The mole fraction of a solution in chemistry.
The characteristic function of a subset in mathematics

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

From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.