The American Heritage® Dictionary of the English Language: Fourth Edition. 2000.
Appendix I
Indo-European Roots
ENTRY:
okw-
DEFINITION:
To see. Oldest form *3ekw-, colored to *3okw-, zero-grade *3kw-. Derivatives include eye, daisy, window, inoculate, and autopsy. 1a.eye; daisy, from Old English age, eye; b.walleyed, window, from Old Norse auga, eye; c.ogle, from Low German oog,oge, eye. a–c all from Germanic *augn- (with taboo deformation). 2. Suffixed form *okw-olo-.a.eyelet, ocellus, ocular, oculist, oculus, ullage; antler, inoculate, monocle, oculomotor, pinochle, from Latin oculus, eye; b.inveigle, from French aveugle, blind, from Gallo-Latin compound *ab-oculus, blind, calqued on Gaulish exs-ops, blind. 3. Form *okw-s.ceratopsian, metopic, myopia, nyctalopia, Pelops, phlogopite, prosopography, prosopopoeia, pyrope, triceratops, from Greek ps, eye (and stem *op-, to see). 4. Suffixed form *okw-ti-.opsin, –opsis, –opsy; autopsy, dropsy, iodopsin, rhodopsin, synopsis, from Greek opsis, sight, appearance. 5. Suffixed form *okw-to-.optic; diopter, optoelectronics, optometry, panoptic, from Greek optos, seen, visible. 6. Suffixed form *okw--.metope, from Greek op, opening. 7. Suffixed form *okw-m.ommatidium, ommatophore, from Greek omma (< *opma), eye. 8. Suffixed form *okw-tro-.catoptric, from Greek katoptron, “back-looker,” mirror (kata-, down, back; see kat-). 9. ophthalmo-; exophthalmos, from Greek ophthalmos, eye (with taboo deformation). 10. Zero-grade form *kw-, in compounds (see ant-, ter-, ghwer-). (Pokorny ok- 775.)
3ekw-, colored to *
age, eye; b. walleyed, window, from Old Norse auga, eye; c. ogle, from Low German oog, oge, eye. a–c all from Germanic *aug
n- (with taboo deformation). 2. Suffixed form *okw-olo-. a. eyelet, ocellus, ocular, oculist, oculus, ullage; antler, inoculate, monocle, oculomotor, pinochle, from Latin oculus, eye; b. inveigle, from French aveugle, blind, from Gallo-Latin compound *ab-oculus, blind, calqued on Gaulish exs-ops, blind. 3. Form *okw-s. ceratopsian, metopic, myopia, nyctalopia, Pelops, phlogopite, prosopography, prosopopoeia, pyrope, triceratops, from Greek 
-. metope, from Greek op
. ommatidium, ommatophore, from Greek omma (< *opma), eye. 8. Suffixed form *okw-tro-. catoptric, from Greek katoptron, “back-looker,” mirror (kata-, down, back; see kat-). 9. ophthalmo-; exophthalmos, from Greek ophthalmos, eye (with taboo deformation). 10. Zero-grade form *
- 775.) 
