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)
: one of the elements corresponding to a small simple eye that make up the compound eye of an arthropod
ommatidial 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 examples are programmatically compiled from various online sources to illustrate current usage of the word 'ommatidium.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


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

First Known Use

1884, in the meaning defined above

Time Traveler
The first known use of ommatidium was in 1884

Dictionary Entries Near ommatidium

Cite this Entry

“Ommatidium.” Dictionary, Merriam-Webster, Accessed 24 Apr. 2024.

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