What does "ommatidium" mean?

One of the conical substructures which make up the eyes of invertebrates with compound eyes.

How do you pronounce "ommatidium"?

Pronounced //ɑməˈtɪdɪəm//.

//ɑməˈtɪdɪəm// noun

noun ·Rare ·Advanced level

Noun

1
One of the conical substructures which make up the eyes of invertebrates with compound eyes.
"The ‘compound’ eyes of insects [...] are made up of large numbers of facets or ommatidia, and in this sense, our own eyes are ‘simple’."
2
any of the numerous small cone-shaped eyes that make up the compound eyes of some arthropods wordnet

"The ‘compound’ eyes of insects [...] are made up of large numbers of facets or ommatidia, and in this sense, our own eyes are ‘simple’."

From Ancient Greek ὀμματίδιον (ommatídion, “little eye”), equivalent to ὄμμα (ómma, stem ὄμματ-) + -idium.

Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.