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.

---

Other Word Forms

• subeffectiveness
  noun
• supereffectiveness
  noun
• uneffectiveness
  noun

Etymology

Origin of effectiveness

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

Example Sentences

The agency first approved mifepristone in 2000, after evaluation of rigorous studies demonstrating its effectiveness and safety.

From Slate • May 4, 2026

The median length of antidepressant treatment in the U.S. is five years, another study found, despite limited evidence about the effectiveness of such long-term use.

From The Wall Street Journal • May 4, 2026

They issued a report reimagining the state superintendent as a student “champion” who would analyze and report on the effectiveness of the education system and also take on an advocacy role.

From Los Angeles Times • May 1, 2026

Investors and economists can argue about the effectiveness and fairness of that policy, but it has insulated America from cars built with low-cost Chinese labor from flooding the market.

From Barron's • Apr. 24, 2026

And I judge the effectiveness of that job not so much by obedience to rule, for rules can be enforced, but by the humor of the general prison population.

From "Newjack: Guarding Sing Sing" by Ted Conover

Related Words

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