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
ˈhärm-fə-lē How to pronounce harmful (audio)
adverb
harmfulness noun

Synonyms of harmful

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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.
Xenex LightStrike Infections acquired inside hospitals remain a serious problem, especially when harmful germs survive on surfaces after a patient leaves a room. — Atharva Gosavi, Interesting Engineering, 30 Aug. 2026 But if the reason you’re being drawn to improve your appearance comes from a place of in inadequacy and constant comparison to others, then this motivation may leave you at risk of developing restrictive or harmful behaviors. — Jennifer Donnelly, Scientific American, 30 Aug. 2026 One of the most devestating aspects of modern medicine and drug development is the constantly evolving nature of harmful pathogens and bacteria. — Dr. Sai Balasubramanian, Forbes.com, 30 Aug. 2026 Their views ranged from seeing the gathering as pointless to potentially harmful for battleground candidates. — Zac Anderson, USA Today, 28 Aug. 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

Rhymes for harmful

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Browse Nearby Words

harmer
harmful
harmfully
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Cite this Entry

“Harmful.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/harmful. Accessed 1 Sep. 2026.

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Kids Definition

harmful

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

Legal Definition

harmful

adjective
harm·​ful
: of a kind likely to cause harm
harmfully adverb
harmfulness noun
Last Updated: - Updated example sentences
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