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o·paque (ō-pāk)
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adj.
1.
a. Impenetrable by light; neither transparent nor translucent.
b. Not reflecting light; having no luster: an opaque finish.
2. Impenetrable by a form of radiant energy other than visible light: a chemical solution opaque to x-rays.
3.
a. So obscure as to be unintelligible: "opaque, elusive, minimal meanings" (John Simon).
b. Mentally obtuse; dense.
n.
Something that is opaque, especially an opaque pigment used to darken parts of a photographic print or negative.
[Middle English opake, shady, and French opaque, opaque (from Old French, shady), both from Latin opācus.]
o·paquely adv.
o·paqueness n.
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:

    Indo-European Roots

    Semitic Roots

    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.

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