1. efficacy

noun. ['ˈɛfɪˌkæsi'] capacity or power to produce a desired effect.


  • efficacious
  • inefficacious
  • effectiveness
  • effectuality
  • effectualness
  • efficaciousness


  • efficacious
  • ineffectiveness
  • inefficacious
  • powerlessness


  • efficacia (Latin)

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Rhymes with Efficacy

  • profligacy

How do you pronounce efficacy?

Pronounce efficacy as ˈɛfɪˌkæsi.

US - How to pronounce efficacy in American English

UK - How to pronounce efficacy in British English

Sentences with efficacy

1. Noun, singular or mass
You can use borax as a weed killer, but you must follow careful guidelines for efficacy and safety.

Quotes about efficacy

1. For books are not absolutely dead things, but do contain a potency of life in them to be as active as that soul was whose progeny they are; nay, they do preserve as in a vial the purest efficacy and extraction of that living intellect that bred them.
- John Milton, Areopagitica

2. I should attempt to treat human vice and folly geometrically... the passions of hatred, anger, envy, and so on, considered in themselves, follow from the necessity and efficacy of nature... I shall, therefore, treat the nature and strength of the emotion in exactly the same manner, as though I were concerned with lines, planes, and solids.
- Baruch Spinoza, Ethics