harmful

adjective

harm·​ful ˈhärm-fəl How to pronounce harmful (audio)
: of a kind likely to be damaging : injurious
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.
Some of these harmful ideologies might be downstream of these larger root causes. ArsTechnica, 30 May 2025 The jury is still out on whether emulsifiers are harmful to the gut. Fran Kritz, Verywell Health, 30 May 2025 China has gone even further, requiring digital watermarks on synthetic media and directing platforms to swiftly remove harmful content — part of its broader strategy of centralized content control. Anisha Sircar, Forbes.com, 30 May 2025 Exposure to harmful substances, like UV rays from the sun, can also damage skin. Heidi Cope, Health, 29 May 2025 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 4 Jun. 2025.

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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