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ommatidium Syllabification: om·ma·tid·i·um
Pronunciation: /ˌäməˈtidēəm/

Definition of ommatidium in English:

noun (plural ommatidia-ˈtidēə)

Each of the optical units that make up a compound eye, as of an insect.
Example sentences
  • In contrast, myriapods and chelicerates mostly lack compound eyes and the ommatidia of the few groups that have compound eyes are very different from insect/crustacean ommatidia.
  • In all these animals, the larval eye continues to exist as part of the adult eye, although the number of ommatidia in the adult compound eye far exceeds the larval quantity.
  • The retina of the compound eye is organized into approximately 3000 functional units or ommatidia, each containing eight photoreceptor cells.


Pronunciation: /-ˈtidēə/
Example sentences
  • The hyperactivation of the Sevenless RTK-signaling pathway in the Drosophila eye causes the ommatidial precursors to differentiate as neurons and results in a rough eye phenotype.
  • The receptors of the midband which, based on structural evidence, are thought to be specialized to detect and analyze polarized light are in the two most ventral ommatidial rows.
  • However, ommatidial rotation is abnormal in GMR-upd compared to wild type, which is best assessed in the schematics of the WT and GMR-upd adult sections.


Late 19th century: modern Latin, from Greek ommatidion, diminutive of omma, ommat- 'eye'.

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