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

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

Proteases, enzymes that recycle proteins, can rapidly cut peptides into individual amino acids, shortening their effectiveness.

From Science Daily • Apr. 28, 2026

It is the cost of that kind of technology, and its relative effectiveness, that must be compared with the cost and effectiveness of the vaccine.

From "The Lives of a Cell" by Lewis Thomas

Related Words

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