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.
In order to rule in her favor, jurors will have to parse the harmful actions of fellow users — including her high school bullies and adult men sending her unsolicited nudes — from design decisions made by the companies themselves. Sonja Sharp, Los Angeles Times, 9 Feb. 2026 Many of these jars contain unknown or poorly documented chemical mixtures that could be toxic to humans or harmful to the specimens themselves if disturbed. Neetika Walter, Interesting Engineering, 9 Feb. 2026 Pests can also be particularly harmful to tender, young plant stems. Patricia Shannon, Southern Living, 9 Feb. 2026 The system responded within milliseconds, fast enough to support real-time reactions such as pulling away from harmful contact or reducing applied force during interaction. New Atlas, 8 Feb. 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 10 Feb. 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

Last Updated: - Updated example sentences
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