harmful
Americanadjective
adjective
Other Word Forms
Etymology
Origin of harmful
First recorded before 1000; Middle English; Old English hearmful; see 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.
While advice on diet and exercise could be helpful to some users, it can be harmful to someone with an eating disorder.
From The Wall Street Journal • Jul. 11, 2026
Once that protective barrier is compromised, harmful microbial products can enter the bloodstream, reach the liver, and trigger inflammatory immune responses, including excessive activation of CD8+ T cells.
From Science Daily • Jul. 11, 2026
Some might look at the Platner implosion and realize that treating each one of his bad decisions, harmful actions, and personal failures as an upside for his relatability backfired spectacularly.
From Slate • Jul. 8, 2026
The EU has a bolstered legal weaponry to tackle harmful online content for children, which makes the European Commission the bloc's digital watchdog.
From Barron's • Jul. 6, 2026
The many wild species not represented among the 157 selected are ones that would have been useless or harmful to people, including all of the most toxic weed species in the environment.
From "Guns, Germs, and Steel: The Fates of Human Societies" by Jared M. Diamond
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.
