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ef·fi·ca·cious (ĕf′ĭ-kāshəs)
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adj.
Producing or capable of producing a desired effect. See Synonyms at effective.
[From Latin efficāx, efficāc-, from efficere, to effect; see EFFECT.]
ef′fi·cacious·ly adv.
ef′fi·cacious·ness n.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. 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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