harmful

adjective

harm·​ful ˈhärm-fəl How to pronounce harmful (audio)
Synonyms of harmfulnext
: of a kind likely to be damaging : injurious
harmful chemicals
harmfully adverb
harmfulness noun

Examples of harmful in a Sentence

DDT has been proven to be extremely harmful to the environment.
Recent Examples on the Web
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.
The brush fire burn is important because Hayes said some trees are harmful to the prairie. Jeff Vorva, Chicago Tribune, 26 Apr. 2026 Could agents create harmful workflows on their own without the company’s help? Stephen Clark, ArsTechnica, 25 Apr. 2026 Noises louder than 85 decibels are considered harmful to humans. Harrison Mantas, Fort Worth Star-Telegram, 25 Apr. 2026 The emphasis on human rights throughout the Adelphi Charter addresses the problem of pharmaceutical patents that raise prices and culturally harmful patents on traditional knowledge. Encyclopedia Britannica, 24 Apr. 2026 See All Example Sentences for harmful

Word History

First Known Use

14th century, in the meaning defined above

Time Traveler
The first known use of harmful was in the 14th century

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Cite this Entry

“Harmful.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/harmful. Accessed 29 Apr. 2026.

Kids Definition

harmful

adjective
harm·​ful ˈhärm-fəl How to pronounce harmful (audio)
: causing damage : injurious
harmfully adverb
harmfulness noun

Legal Definition

harmful

adjective
harm·​ful
: of a kind likely to cause harm
harmfully adverb
harmfulness noun

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