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.
Because cPLA2 also supports healthy brain function, scientists needed to find a way to reduce its harmful activity without completely shutting the enzyme down.
From Science Daily • May 26, 2026
Officials have also emphasized that the crisis did not result in the release of chemicals that could be harmful.
From Los Angeles Times • May 26, 2026
A key provision calls for wiping memory between sessions, specifically to prevent chatbots from building on harmful mental states over time.
From The Wall Street Journal • May 25, 2026
While tarantulas can deliver a painful bite, they are not considered harmful to humans.
From BBC • May 22, 2026
After some wrangling, J. T. promised Venkatesh unfettered access to the gang’s operations as long as J. T. retained veto power over any information that, if published, might prove harmful.
From "Freakonomics: A Rogue Economist Explores the Hidden Side of Everything" by Steven D. Levitt
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.
