harmful
Americanadjective
adjective
Other Word Forms
- harmfully adverb
- harmfulness noun
- quasi-harmful adjective
- quasi-harmfully adverb
- unharmful adjective
- unharmfully adverb
Etymology
Origin of harmful
First recorded before 1000; Middle English; Old English hearmful; harm, -ful
Explanation
Things that are harmful hurt people, or are likely to hurt them. Listening to loud music through headphones can be harmful to your hearing. Harmful is an adjective that comes in handy when you're talking about things that cause injury to someone or damage something. Burning coal can be harmful to the environment, and eating too much candy can be harmful for your teeth. Harmful words can hurt someone's feelings and harmful actions might put them in danger. The Old English hearm, "hurt, evil, or grief," is at the root of harmful.
Vocabulary lists containing harmful
Earth Day
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Unfavorable
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Researchers at the Fraunhofer Institute for Cell Therapy and Immunology IZI in Halle identified a substance that targets harmful pathogens without affecting the rest of the microbial community.
From Science Daily • Apr. 13, 2026
On the flip side, a sustained spike in fuel prices could be particularly harmful for JetBlue and Frontier’s margins, he notes.
From Barron's • Apr. 12, 2026
Anything harmful shouldn't be kept secret, but "if you're planning a surprise for them or present, yeah," Caitlin said.
From BBC • Apr. 12, 2026
Proponents of raw milk say that pasteurization, a heating process that kills harmful bacteria, removes natural health benefits and that warnings around the consumption of raw milk are overstated.
From The Wall Street Journal • Apr. 11, 2026
Storage in human beings has been well investigated, and we know that the average person is storing potentially harmful amounts.
From "Silent Spring" by Rachel Carson
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
