Omicron

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. It is rarely used in mathematics because it is indistinguishable from the Latin letters O, o and easily confused with the digit 0. This letter is derived from the Phoenician letter ayin . In classical Greek, omicron represented the sound in contrast to omega . In modern Greek, omicron represents the sound . Letters that arose from omicron include Roman O and Cyrillic O.

In Unicode the capital letter is codepoint U+039F and the lowercase is U+03BF.

The upper-case letter of omicron (O) was originally used in mathematics as a symbol for Big O notation, representing the asymptotic rate of growth of a function.

Read more about Omicron:  In Popular Culture