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.
Harmful use may occur without their knowledge since the work is classified, workers said in the letter.
From Los Angeles Times • May 1, 2026
Harmful environments or substances can worsen your response to an exposure.
From The Wall Street Journal • Jan. 19, 2026
Harmful algal blooms have been reported on every continent except Antarctica.
From Salon • Aug. 16, 2025
Harmful acetaldehyde accumulated less in these mice, and they exhibited greatly reduced stress reactions in their livers, which was reflected in better blood values.
From Science Daily • May 13, 2024
Edsger W. Dijkstra's note in the March 1968 `Communications of the ACM', "Goto Statement Considered Harmful", fired the first salvo in the structured programming wars.
From The Jargon File, Version 2.9.10, 01 Jul 1992 by Raymond, Eric S.
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.
