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.
That might help researchers discover which technology helps what kinds of people best and which makes no impact or is harmful to brain health. Nicole Villalpando, Austin American Statesman, 30 July 2025 McNair said any delay in response from school officials and emergency responders are especially harmful. Edward Lee, Baltimore Sun, 29 July 2025 The layer in the upper atmosphere protects the planet from the Sun's radiation, but ozone that forms at ground level—caused by a chemical reaction in the sunlight between pollutants such as car exhaust fumes and power plant emissions—is harmful. Chloe Mayer, MSNBC Newsweek, 29 July 2025 Pavi, like the many disabled characters in the Avatar universe that came before her, can serve as a reminder that inclusivity isn’t harmful to good storytelling but is a key part of it. Braedon Montgomery, Forbes.com, 29 July 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

Browse Nearby Words

Cite this Entry

“Harmful.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/harmful. Accessed 4 Aug. 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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