Definitions

from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun Power or capacity to produce a desired effect; effectiveness.

from The Century Dictionary.

  • noun The quality of being efficacious or effectual; production of, or the capacity of producing, the effect intended or desired; effectiveness.
  • noun Synonyms Efficiency, etc. (see effectiveness); virtue, force, energy.

from the GNU version of the Collaborative International Dictionary of English.

  • noun Power to produce effects; operation or energy of an agent or force; production of the effect intended

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun uncountable Ability to produce a desired amount of a desired effect.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun capacity or power to produce a desired effect

Etymologies

from The American Heritage® Dictionary of the English Language, 4th Edition

[Latin efficācia, from efficāx, efficāc-, efficacious; see efficacious.]

from Wiktionary, Creative Commons Attribution/Share-Alike License

From Latin efficacia ("efficacy"), from efficax ("efficacious"); see efficacious.

Examples

Comments

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  • Don't confuse with effective. They will know that you are impersonating a serious grad student.

    June 28, 2008