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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