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.
Social media companies continue to promote harmful content without consequence. Jeffrey Sonnenfeld, Time, 13 Jan. 2026 Part of the researchers’ message is that exposure to harmful substances doesn’t just come from smokestacks or car exhaust. Scott Lafee, San Diego Union-Tribune, 13 Jan. 2026 Fargeorge was taken into custody on Saturday and charged with harmful communication with a minor. Staff Report, Hartford Courant, 13 Jan. 2026 Sundays’ solution is this sofa, which is stain-resistant, moisture-repellent, fully washable, and non-toxic—the stain-repellent treatment is made without chemicals that might be harmful to the smaller members of your household. Elly Leavitt, Vogue, 13 Jan. 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

Browse Nearby Words

Cite this Entry

“Harmful.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/harmful. Accessed 21 Jan. 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

More from Merriam-Webster on harmful

Last Updated: - Updated example sentences
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