Omicron Ο
Omicron (uppercase Ο, lowercase ο, literally "small o": Όμικρον, o mikron, micron meaning 'small' in contrast to omega) is the 15th letter of the Greek alphabet. In the system of Greek numerals it has a value of 70. This letter is derived from the Phoenician letter ayin
. In classical Greek, omicron represented the sound [o] in contrast to omega [ɔː] and ου [oː]. In modern Greek, omicron represents the mid back rounded vowel /o/. Letters that arose from omicron include Roman O and Cyrillic O.