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.
For example, the Oeko-Tex Standard 100 applies to bedding that is free of harmful chemicals. Nashia Baker, Architectural Digest, 27 Aug. 2025 Electronic harassment, or online harassment, refers to the use of electronic communication devices to target an individual with threatening, intimidating, or harmful behavior. Shania Russell, EW.com, 27 Aug. 2025 Cyanogenic glycosides found in flaxseed may be harmful if consumed in excess. Brittany Lubeck, Verywell Health, 27 Aug. 2025 The legislation was justified initially as part of a package of measures to protect the climate from harmful CO2 emissions. Neil Winton, Forbes.com, 27 Aug. 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 9 Sep. 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!