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

Scientists plan to continue refining these compounds to improve their effectiveness and explore their potential as future medicines.

From Science Daily • Apr. 21, 2026

In March 2025, Kennedy issued a statement that noted vaccines’ effectiveness in preventing measles’ spread, but stopped short of outright recommending that parents vaccinate their children.

From Los Angeles Times • Apr. 16, 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

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

Then Ambady compared those snap judgments of teacher effectiveness with evaluations of those same professors made by their students after a full semester of classes, and she found that they were also essentially the same.

From "Blink" by Malcolm Gladwell

Related Words

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