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.
The number of contaminants overall is one thing, but many different constituents can be considered contaminants, and some are harmful at all levels, while some are not harmful at lower levels. Jasmine Laws, MSNBC Newsweek, 13 Oct. 2025 Many dyes rely on mordants—metallic salts used to fix color to fabric—that can range from benign to environmentally harmful. Alexandra Harrell, Sourcing Journal, 13 Oct. 2025 The lake is much cleaner now after restoration efforts, but there are still signs warning that its fish may be harmful to eat. Eva Roytburg, Fortune, 11 Oct. 2025 This will keep your pieces safe from harmful humidity or worse. Mary Cornetta, Better Homes & Gardens, 11 Oct. 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 18 Oct. 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
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