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.
Diabetes can also weaken the brain’s protective barrier, letting harmful substances in.
From Science Daily • Jun. 17, 2026
"We also combine automated systems and human review to identify and block harmful material", it added in a statement.
From BBC • Jun. 17, 2026
This is mainly due to technology and workplace requirements, but it is also a response to jeremiads about the sun’s harmful rays.
From The Wall Street Journal • Jun. 16, 2026
There were also die-offs of seals, sea lions and marine birds, Leising said, probably from a combination of a lack of food and harmful algal blooms, and less food out there for baleen whales.
From Los Angeles Times • Jun. 15, 2026
“Brittani Slocum. First question. The pageant has come under fire for perpetuating an unrealistic image of superthin girls as beautiful, and many people feel this is harmful to girls’ self-esteem.
From "Beauty Queens" by Libba Bray
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.
