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.
Asked about those concerns, Senate Majority Leader Bob Duff, D-Norwalk, said the legislation is needed, adding the bill outlines helpful and harmful AI applications simultaneously. P.r. Lockhart, Hartford Courant, 17 May 2026 Their deaths were not inevitable — they were exposed to, and in many cases were pushed harmful content online, the kind any child could encounter. Stephanie Petit, PEOPLE, 17 May 2026 But wildlife and pollinators don't coexist well with harmful chemicals. Lauren David, Better Homes & Gardens, 17 May 2026 The podcast discussed a number of discredited ideas, including that mRNA vaccines may contain harmful DNA contaminants. Matthew Perrone, Fortune, 16 May 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 21 May. 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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