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 next step will be larger Phase III clinical trials designed to confirm the drug's safety and effectiveness in a broader patient population before regulators consider approval.

From Science Daily • May 27, 2026

Reports of children in Australia being able to access sites supposedly blocked for under-16s have raised concerns over the law's effectiveness.

From BBC • May 25, 2026

There was no difference in effectiveness between neutral and affirming debunkbots, whereas when the debunkbot was condescending, it was somewhat less effective at reducing conspiracy beliefs.

From The Wall Street Journal • May 24, 2026

In other remarks, he emphasized what he called “lethality over likability,” arguing that military leadership must prioritize combat readiness and battlefield effectiveness over cultural or institutional concerns.

From Salon • May 24, 2026

The organism remains viable in the soil for years and therefore be comes to all intents and purposes permanently established, increasing in effectiveness, and being continuously spread by natural agencies.

From "Silent Spring" by Rachel Carson

Related Words

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