Dictionary.com
Thesaurus.com

omicron

American  
[om-i-kron, oh-mi-] / ˈɒm ɪˌkrɒn, ˈoʊ mɪ- /

noun

  1. the 15th letter of the Greek alphabet (O,o ).

  2. the vowel sound represented by this letter.


omicron British  
/ ˈɒmɪkrɒn, əʊˈmaɪkrɒn /

noun

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

"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

Etymology

Origin of omicron

< Greek ō mikrón, literally, small o. Cf. omega

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

See Examples For:

Washington’s manic quarantining of cruise-ship passengers, its restricting of foreign entry, probably did next to nothing to slow spread until a vaccine and the less-virulent omicron variants arrived, which took a year.

From The Wall Street Journal Aug. 7, 2026

A show-threatening omicron shutdown, illness and the loss of Adam, who passed away at the end of April 2023.

From Los Angeles Times May 29, 2024

The researchers measured how many of the participants' neutralizing antibodies were specific for the original variant, the omicron variant or both.

From Science Daily May 17, 2024

This decline was evident among those infected in the early phase of the pandemic and those infected when the delta and omicron variants were dominant.

From Salon Mar. 12, 2024

During the peak of ancient astronomy, Greek astronomical tables regularly employed zero; its symbol was the lowercase omicron, o, which looks very much like our modern-day zero, though it’s probably a coincidence.

From "Zero: The Biography of a Dangerous Idea" by Charles Seife

Vocabulary.com logo
by dictionary.com

Join 12,000,000 vocabulary learners

Start learning new words today on VocabTrainer.
You'll remember them forever.

Start training