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

There’s a chunk of code for a memory system to keep the context of conversations going without overloading the AI with too much information—a problem known to amplify hallucinations and reduce the effectiveness of guardrails.

From The Wall Street Journal • Apr. 17, 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

Howard Fuller knew that if whites considered Operation Breakthrough as an exclusively “black” organization, it would limit the group’s effectiveness.

From "The Best of Enemies" by Osha Gray Davidson

Related Words

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