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.
Fires that burn at low temperature produce more harmful gases than hot fires. Eric Niiler, Los Angeles Times, 6 July 2026 Public health data has taught us that alcohol, which can be fine when consumed in moderation, can be harmful to individual and societal health in excessive amounts. Adam Hoffer, Chicago Tribune, 5 July 2026 Think of it as skincare in disguise, locking in at least 12 hours of moisture while shielding you from harmful UV rays. Tanya Sharma, InStyle, 4 July 2026 With code purple and code red, which is one step less dangerous than purple, everyone is at risk for harmful health impacts, according to WUSA9, a local TV news station tracking air quality. Karissa Waddick, USA Today, 4 July 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 6 Jul. 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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