, 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
and easily confused with the digit 0
. This letter is equal to the Phoenician letter Ayin. In modern Greek
, Omicron represents the sound ɔː.
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 as a symbol for Big O notation, representing the asymptotic rate of growth of a function in mathematics.