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Webster 1913 Edition

efficacy

ef′fi-ca-cy

,
Noun.
[L.
efficacia
, fr.
efficax
. See
Efficacious
.]
Power to produce effects; operation or energy of an agent or force; production of the effect intended;
as, the
efficacy
of medicine in counteracting disease; the
efficacy
of prayer.
“Of noxious efficacy.”
Milton.

Syn. – efficacy.
Syn. – Virtue; force; energy; potency; efficiency.

Webster 1828 Edition

Efficacy

EF'FICACY

,
Noun.
[L. efficax.] Power to produce effects;production to the effect intended; as the efficacy of the gospel in converting men from sin; the efficacy of prayer; the efficacy of medicine in counteracting disease; the efficacy of manure in fertilizing land.

Definition 2024

efficacy

efficacy

English

Noun

efficacy ‎(uncountable)

  1. Ability to produce a desired effect under ideal testing conditions.
    • 2005, Flay et al. Standards of Evidence: Criteria for Efficacy, Effectiveness and Dissemination DOI: 10.1007/s11121-005-5553-y
      Efficacy refers to the beneficial effects of a program or policy under optimal conditions of delivery, whereas effectiveness refers to effects of a program or policy under more real-world conditions.
  2. Degree of ability to produce a desired effect.
    • 1996, Moskovich, Patent application PCT/US1996/003658
      Toothbrush with improved efficacy
    • Wikipedia entry for "vaccine efficacy", as of 2016
      Vaccine efficacy is the percentage reduction of disease in a vaccinated group of people compared to an unvaccinated group, using the most favorable conditions.
  3. Ability to produce a desired amount of a desired effect.

Synonyms

Related terms

Translations

External links

  • efficacy in Webster’s Revised Unabridged Dictionary, G. & C. Merriam, 1913
  • efficacy in The Century Dictionary, The Century Co., New York, 1911

Etymology

From Old French efficace, from Late Latin efficacia ‎(“efficacy”), from Latin efficax ‎(“efficacious”); see efficacious.

Pronunciation

  • IPA(key): /ˈɛf.ɪ.kə.si/

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