[om-i-kron, oh-mi-]


the 15th letter of the Greek alphabet (O, o).
the vowel sound represented by this letter.

Origin of omicron

< Greek ō mikrón, literally, small o. Cf. omega Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for omicron

Historical Examples of omicron

  • Mira, (Omicron Ceti,) in the neck of the Whale, is a variable star.

    Letters on Astronomy

    Denison Olmsted

  • Newton presented him with one of his publications, entitled "Omicron."

  • At all events, it was not possible for him to think of anything bad when he called “Omicron.”

  • Omicron must show her face in the stars from time to time to remind the child of his love.

  • And then, on the following morning, Sir Omicron also went his way.

    Doctor Thorne

    Anthony Trollope

British Dictionary definitions for omicron



the 15th letter in the Greek alphabet (Ο, ο), a short vowel, transliterated as o

Word Origin for omicron

from Greek ō mikron small o; see micro-, omega
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for omicron

15th letter of the Greek alphabet, literally "small 'o,' " from Greek (s)mikros "small," from PIE *smik-. Because the vowel was "short" in ancient Greek. Cf. Omega.

Online Etymology Dictionary, © 2010 Douglas Harper

omicron in Medicine


[ŏmĭ-krŏn′, ōmĭ-]


The 15th letter of the Greek alphabet.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.