om·​ma·​tid·​i·​um | \ ˌä-mə-ˈti-dē-əm How to pronounce ommatidium (audio) \
plural ommatidia\ ˌä-​mə-​ˈti-​dē-​ə How to pronounce ommatidium (audio) \

Definition of ommatidium

: one of the elements corresponding to a small simple eye that make up the compound eye of an arthropod

Other Words from ommatidium

ommatidial \ ˌä-​mə-​ˈti-​dē-​əl How to pronounce ommatidium (audio) \ adjective

Examples of ommatidium in a Sentence

Recent Examples on the Web In this kind of compound eye, each ommatidium has to be encased in something that blocks light in order to isolate it from the neighboring ommatidia, keeping each unit distinct. Scott K. Johnson, Ars Technica, 15 Aug. 2020 At the top of each ommatidium is a lens, with cone cells beneath it that also help focus incoming light. Scott K. Johnson, Ars Technica, 15 Aug. 2020 The tiny organ contains 100 ommatidia, or subunits that make up compound eyes found today in many insects, surrounding a light-sensing structure called a rhabdom. Jason Daley, Smithsonian, 11 Dec. 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'ommatidium.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of ommatidium

1884, in the meaning defined above

History and Etymology for ommatidium

New Latin, from Greek ommat-, omma eye; akin to Greek ōps eye — more at eye

Learn More About ommatidium

Time Traveler for ommatidium

Time Traveler

The first known use of ommatidium was in 1884

See more words from the same year

Dictionary Entries Near ommatidium




See More Nearby Entries 

Statistics for ommatidium

Cite this Entry

“Ommatidium.” Dictionary, Merriam-Webster, Accessed 2 Oct. 2022.

Style: MLA
MLACheck Mark Icon ChicagoCheck Mark Icon APACheck Mark Icon Merriam-WebsterCheck Mark Icon

More from Merriam-Webster on ommatidium Encyclopedia article about ommatidium


Test Your Vocabulary

Challenging Words You Should Know

  • hedgehog reading a book
  • Often used to describe “the march of time,” what does inexorable mean?
Spell It

Can you spell these 10 commonly misspelled words?

Universal Daily Crossword

A daily challenge for crossword fanatics.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!