Omicron

n. 15th letter of Greek alphabet

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 not used in mathematics because it is indistinguishable from the Latin letter O. Indeed, it is not widely used because of confusion with the digit 0. This letter is equal to the Phoenician letter Ayin. It is also most similar to the modern English letter O, as in 'hot'.
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Noun
1. the 15th letter of the Greek alphabet
(hypernym) letter, letter of the alphabet, alphabetic character
(member-holonym) Greek alphabet

n. omicron, 15th letter of Greek alphabet

     moronic