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 and "qōph" represented sounds that were not distinctive in Greek—at most, they may have been identified with allophones determined by the following vowel. The letter qoppa was used in certain Greek dialects (notably the western dialects, which ultimately gave rise to Etruscan and eventually the Latin alphabet), but elsewhere dropped out of general use. It is possible that qoppa had been assigned to the Ancient Greek , and when that sound shifted to , the letter qoppa continued as the letter phi. Phoenician had three letters, "sāmekh, ṣādē" and "šin", representing three or probably four voiceless sibilant sounds, whereas Greek