harmful

1 of 2

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

harmfulness

2 of 2

noun

harm·​ful·​ness
plural -es
: the quality or state of being harmful

Examples of harmful in a Sentence

Adjective DDT has been proven to be extremely harmful to the environment.
Recent Examples on the Web
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Adjective
Research has shown that raw cheese is not, in fact, resistant to pathogens; while aging can mitigate some risk, harmful bacteria can still survive the usual 60-day maturation process. CNN Money, 14 June 2026 OpenAI is also facing a number of wrongful death lawsuits, which allege that ChatGPT drove users to experience harmful delusions and, in some cases, to commit suicide. Ashley Capoot, CNBC, 13 June 2026 Unlike other hard metals, tungsten is largely nontoxic, but the byproducts from mining it—called tailings—contain other harmful metals including arsenic, copper, zinc and lead and can leach into the environment. Ari Sen, Scientific American, 13 June 2026 The proprietary filtration system is specifically engineered to remove impurities, chlorine, harmful chemicals and heavy metals from your water. ABC News, 13 June 2026 See All Example Sentences for harmful

Word History

First Known Use

Adjective

14th century, in the meaning defined above

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

Browse Nearby Words

Cite this Entry

“Harmful.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/harmful. Accessed 19 Jun. 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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