Synonym Chooser

How does the adjective efficacious contrast with its synonyms?

Some common synonyms of efficacious are effective, effectual, and efficient. While all these words mean "producing or capable of producing a result," efficacious suggests possession of a special quality or virtue that gives effective power.

a detergent that is efficacious in removing grease

When is effective a more appropriate choice than efficacious?

In some situations, the words effective and efficacious are roughly equivalent. However, effective stresses the actual production of or the power to produce an effect.

an effective rebuttal

When would effectual be a good substitute for efficacious?

Although the words effectual and efficacious have much in common, effectual suggests the accomplishment of a desired result especially as viewed after the fact.

the measures to stop the pilfering proved effectual

When can efficient be used instead of efficacious?

While the synonyms efficient and efficacious are close in meaning, efficient suggests an acting or a potential for action or use in such a way as to avoid loss or waste of energy in effecting, producing, or functioning.

an efficient small car

Example Sentences

Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Recent Examples of efficacious Thorne is also rigorously tested and has worked with independent researchers from places like Mayo Clinic and the National Institutes of Health, to ensure its products are high-performance, safe, and efficacious. Vogue, 30 Mar. 2025 Despite Chief Justice Warren formally writing the opinion to apply exclusively to education, its attack on segregation has—paradoxically—been most efficacious beyond that original context. Justin Driver, The Atlantic, 15 Mar. 2025 Oh, that’s right, there’s a measles vaccines that is over 97% efficacious against the measles after two doses are administered, which people have been getting for years. Bruce Y. Lee, Forbes, 15 Mar. 2025 On the other side are patients living with untreated diseases hoping that pharmaceutical companies will soon develop an efficacious treatment. Wayne Winegarden, Forbes, 5 Mar. 2025 See All Example Sentences for efficacious
Recent Examples of Synonyms for efficacious
Adjective
  • Airlines, including United, are working with the FAA to address the issues and ensure safe and efficient air travel.
    Zach Wichter, USA Today, 13 May 2025
  • Regular interaction expands potential deal flow and positions you as a credible and efficient buyer, capable of quickly responding when attractive opportunities arise.
    Paul Davis, Forbes.com, 12 May 2025
Adjective
  • About 50% of Connecticut’s Medicaid expenses in most program areas are covered through federal reimbursement, which would make the effective annual cost to the state about $137.5 million.
    Keith M. Phaneuf, Hartford Courant, 10 May 2025
  • Brown accounted for four of those free-throw attempts, and the rest came from Boston’s effective bench, with Pritchard, Kornet and Kristaps Porzingis making all eight of their first-half freebies.
    Zack Cox, Boston Herald, 10 May 2025
Adjective
  • Fans from America to Europe to Australia bought his books and flocked to his one-man shows, and his potent doses of humor and hard truth enthralled both the highborn and the humble.
    Mary Ann Gwinn, Los Angeles Times, 9 May 2025
  • Fentanyl — a potent and deadly opioid laced into seven out of 10 pills seized by officers — wasn’t out on the street.
    Julia Coin, Charlotte Observer, 8 May 2025

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Cite this Entry

“Efficacious.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/efficacious. Accessed 22 May. 2025.

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