n. pl. oc·u·li (-lī′)
An eyelike opening or ornament, especially:
a. A round window.
b. A circular opening at the apex of a dome.
[Medieval Latin, from Latin, eye; see okw- in the Appendix of Indo-European roots.]
(click for a larger image)oculus
in the dome of the Pantheon
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.