Xi (letter) dialects of most of the Greek mainland and Euboea, the sound [ks] was represented by Χ (which in classical Greek is chi, used for ). Because this variant of the Greek alphabet was used in Italy, the Latin alphabet borrowed Χ rather than Ξ as the Latin letter X. While having no Latin derivative, the Xi was adopted into the early Cyrillic alphabet, as the letter ksi (Ѯ, ѯ). The uppercase letter Ξ is used as symbol for: The lowercase letter ξ is used as a symbol for: These characters are used only as mathematical symbols. Stylized Greek text should
History of the Greek alphabet Phoenician values, but with different forms: as the Greek letter digamma for the consonant , and as the letter upsilon for the vowel . Upsilon was added at the end of the alphabet, perhaps to avoid upsetting the alphabetic order that was used in Greek numerals. Phoenician "hē" had been used as a "mater lectionis" for both and in addition to , but in Greek it was restricted to , following the acrophonic principle; its value was instead written with the letter "’āleph", while Greek was written with "ḥeth". All Phoenician letters had been acrophonic, and they remained so in