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

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

“Skepticism remains over the effectiveness of the cease-fire agreement, leaving the market wary. Any headlines suggesting continued combat could easily trigger another round of dollar buying,” Morimoto says.

From The Wall Street Journal • 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

By analysing millions of their genetic variants, the researchers found a pattern suggesting a link between some variants and the effectiveness of the drugs.

From BBC • Apr. 8, 2026

He practices the things he has been taught, though it is difficult to gauge the effectiveness of his illusions on his own.

From "The Night Circus" by Erin Morgenstern

Related Words

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