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.
Telegram said its moderation systems remove millions of pieces of harmful content each month, including non-consensual pornography. Hanako Montgomery, CNN Money, 22 June 2026 Scientists used to think only UVB was harmful because UVB rays cause sunburns. Guy German, Fortune, 21 June 2026 Many OnlyFans creators took issue with the harmful stereotypes used in Levinson’s depiction of their field, including one scene with Cassie posing spread-eagle in a diaper, with a pacifier in her mouth. Glenn Garner, Deadline, 20 June 2026 Following the recommendations from the NWS helps bolster your safety during air quality alerts, minimizing your exposure to potentially harmful pollutants. Southern California Weather Report, Daily News, 20 June 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 23 Jun. 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

Love words? Need even more definitions?

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

More from Merriam-Webster