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

One example is extensive, independent testing to ensure the effectiveness and reliability of critical systems, which can mean life or death for servicemembers.

From The Wall Street Journal • Apr. 16, 2026

According to media reports, the study used hospital patients’ vaccination status to calculate the success of the season’s vaccine, a method long used to determine flu vaccine effectiveness.

From Los Angeles Times • Apr. 14, 2026

It claimed "stopping full-time pay for part-time work... could increase capacity and the effectiveness of current staff and allow for headcount reduction", which would "save around £270,000".

From BBC • Apr. 9, 2026

Intense competition is pushing manufacturers to improve effectiveness while slashing costs, sometimes to less than $1,000 per unit, making them "affordable", Myronenko said.

From Barron's • Apr. 9, 2026

Livingston also was perplexed about his inability to coax the protons to more than seventy-five accelerating steps, a mysterious constraint on the machine’s effectiveness.

From "Big Science" by Michael Hiltzik

Related Words

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