Omicron (uppercase Ο, lowercase ο, literally "small o": 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. It is rarely use in mathematics because it is indistinguishable from the Latin letter O and easily confused with the digit 0. This letter is equal to the Phoenician letter Ayin. In modern Greek, Omicron represents the sound IPA: [ɔː].