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.
And some types of glyphosates may be more harmful than others. Michal Ruprecht, CNN Money, 24 Feb. 2026 In addition to its harmful systemic effects, consuming alcoholic beverages is linked with the loss of dietary restraint and overconsumption of calories. Anna Giorgi, Verywell Health, 23 Feb. 2026 Abraham’s also long been critical of Covid vaccines, suggesting without providing evidence that the shots are harmful. Erika Edwards, NBC news, 23 Feb. 2026 The longterm impacts of stress are well-researched and understood to be harmful for a variety of organs. Helen Carefoot, Flow Space, 23 Feb. 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 26 Feb. 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

More from Merriam-Webster on harmful

Last Updated: - Updated example sentences
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