effectiveness

American  

[ih-fek-tiv-nis, ee-fek‐] / ɪˈfɛk tɪv nɪs, iˈfɛk‐ /

Rarely effectivity

noun

1. the quality of producing an intended or desired result.

   For maximum effectiveness of your weight loss plan, you need to combine exercise with a healthy diet.

2. the quality of producing a deep or vivid impression.

   We were struck by the evident appeal and effectiveness of these short, dramatic, upbeat video stories.

3. a measure of the success of a vaccine or other pharmaceutical when used in the real world, as opposed to the controlled environment of a clinical trial.

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Other Word Forms

• subeffectiveness noun
• supereffectiveness noun
• uneffectiveness noun

Etymology

Origin of effectiveness

First recorded in 1600–10; effective ( def. ) + -ness ( def. )

Example Sentences

Nine biosimilars — which are FDA-approved drugs with the same safety, effectiveness and treatment benefits as the original drug — flooded the market at substantially lower prices.

From MarketWatch • Apr. 7, 2026

FDA regulations also require the agency to assess both safety and effectiveness before approving a substance for compounding.

From Salon • Apr. 4, 2026

Research by the International Monetary Fund finds that rule of law is necessary for long-term economic growth and that “within the rule of law, the effectiveness of the justice system…are critical to economic outcomes.”

From Barron's • Apr. 1, 2026

Yet Novo Nordisk plans to avoid the mistakes that hurt it during the last round, and will seek to hold on to its early lead by emphasizing the effectiveness of its pill.

From The Wall Street Journal • Apr. 1, 2026

According to a study done by one advertising research firm, whenever there are at least four different 15-second commercials in a two-and-a-half-minute commercial time-out, the effectiveness of any one 15-second ad sinks to almost zero.

From "The Tipping Point" by Malcolm Gladwell

Related Words

• capability
• efficacy
• efficiency
• potency
• power
• success