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.
One study of Character AI found that the app frequently feeds harmful content to children. Brit McCandless Farmer, CBS News, 8 Dec. 2025 In the absence of broad federal legislation, some states have passed laws to address potentially risky and harmful uses of AI, such as the creation of misleading deepfakes and algorithmic discrimination in hiring. Clare Duffy, CNN Money, 8 Dec. 2025 In the immediate term, though, the ambiguity is harmful to the environment for vaccine development. Lisa Jarvis, Twin Cities, 7 Dec. 2025 And if kids do end up spending more time on screens, Christakis said some types of content are less potentially harmful than others. Toria Sheffield, PEOPLE, 7 Dec. 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 12 Dec. 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
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!