effectiveness

American

[ih-fek-tiv-nis, ee-fek‐] / ɪˈfɛk tɪv nɪs, iˈfɛk‐ /

Rarely effectivity

noun

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.
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.
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. )

Vocabulary lists containing effectiveness

Reading: Informational - Middle School

Looking to grow your vocabulary? Check out this interactive, curated word list from our team of English language specialists at Vocabulary.com – one of over 17,000 lists we've built to help learners worldwide!

Media Literacy - High School

Interested in learning more words like this one? Our team at Vocabulary.com has got you covered! You can review flashcards, quiz yourself, practice spelling, and more – and it's all completely free to use!

Media Literacy - Middle School

Want to remember this word for good? Start your learning journey today with our library of interactive, themed word lists built by the experts at Vocabulary.com – we'll help you make the most of your study time!

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

An NHS spokesperson said: "Oral immunotherapy as a treatment for food allergies is not routinely available on the NHS due to limited evidence around the effectiveness of available products."

From BBC • Apr. 23, 2026

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

From Science Daily • Apr. 21, 2026

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

But I was also impressed by the boycott’s effectiveness: after nine days, during which the buses ran empty, the company returned the fare to fourpence.

From "Long Walk to Freedom" by Nelson Mandela

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023