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.
Referred to as financial toxicity, a diagnosis can result in harmful economic burden, stress and debt due to high out-of-pocket medical costs stemming from diagnostic tests, treatments, prescription drugs and hospital stays. — Chicago Tribune, 18 Oct. 2026 Security software may help detect harmful scripts or their effects, although no antivirus product can guarantee protection against every attack. — Kurt Knutsson, FOXNews.com, 17 Oct. 2026 And asking them to engage with new software could be harmful. — Lissa Soep, Vox, 17 Oct. 2026 In March, a jury found Meta and YouTube liable for creating products that led to harmful and addictive behavior by young users. — Mary Cunningham, CBS News, 16 Oct. 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 20 Oct. 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
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