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.
This method takes too long—by the time the soup is fully thawed, there is a high risk that harmful bacteria have already grown. Riley Wofford, Martha Stewart, 16 Mar. 2026 This can introduce impurities or harmful microorganisms to the bathroom environment as a result. Ethan Stone, USA Today, 15 Mar. 2026 Conversely, toxic families are characterized by harmful behaviors that damage the emotional and psychological well-being of family members. Sherri Gordon, Parents, 15 Mar. 2026 In reality, these online communities often promote harmful attitudes and ideologies, which position feminism—that is, the pursuit of gender equality—as a direct threat to men’s sociopolitical status and well-being. Lucy Morgan, Glamour, 13 Mar. 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 Mar. 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

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