Chi (letter) for the design of steel structures. In graph theory, a lowercase chi is used to represent a graph's chromatic number. Chi (letter) Chi (uppercase Χ, lowercase χ; ) is the 22nd letter of the Greek alphabet, pronounced or in English. Its value in Ancient Greek was an aspirated velar stop (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 ( or ) it is pronounced as a voiceless palatal fricative , as
Greek alphabet late ninth century BC or early eighth century BC, the Greek alphabet emerged. The period between the use of the two writing systems, during which no Greek texts are attested, is known as the Greek Dark Ages. The Greeks adopted the alphabet from the earlier Phoenician alphabet, one of the closely related scripts used for the West Semitic languages. However, the Phoenician alphabet is limited to consonants. When it was adopted for writing Greek, certain consonants were adapted to express vowels. The use of both vowels and consonants makes Greek the first alphabet in the narrow sense, as distinguished from