different between effectiveness vs efficacy

English

Etymology

effective +? -ness

Pronunciation

Noun

effectiveness (countable and uncountable, plural effectivenesses)

1. The property of being effective, of achieving results.

   The effectiveness of the drug was well established.

2. The capacity or potential for achieving results.
3. The degree to which something achieves results.

   He questioned the effectiveness of the treatment.

   • 2013, Phil McNulty, "[1]", BBC Sport, 1 September 2013:

     United were having more possession but a sign of the effectiveness of Liverpool's defence was that it took the visitors 76 minutes to force Mignolet into serious action, when he dived to punch away a shot from substitute Nani.

Related terms

• effect
• effective
• effectivity
• effector
• effectual
• effectuate
• efficacious
• efficacity
• efficacy
• efficiency
• efficient

Translations

English

Etymology

From Old French efficace, from Late Latin effic?cia (“efficacy”), from effic?x (“efficacious”); see efficacious.

Pronunciation

• IPA^(key): /??f.?.k?.si/

Noun

efficacy (usually uncountable, plural efficacies)

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

Synonyms

• efficacity

Related terms

Translations

Further reading

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