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Definitions

harmful

[hahrm-fuhl] / ˈhɑrm fəl /
ADJECTIVE
injurious, hurtful
Synonyms
STRONGEST
adverse bad catastrophic damaging destructive detrimental disadvantageous disastrous inimical noxious painful pernicious risky ruinous sinful toxic unhealthy unsafe
WEAK
baleful baneful calamitous cataclysmic consumptive corroding corrupting crippling deleterious dire evil harassing incendiary internecine malefic malicious malignant menacing mischievous murderous nocuous pestiferous pestilential sinister subversive undermining unwholesome virulent
Antonyms
STRONGEST
advantageous aiding assisting beneficial favorable fortunate good harmless healthy helpful honest kind lucky profitable safe upright

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.

In this process, harmful bacteria such as Porphyromonas gingivalis often regain dominance quickly because they thrive in inflamed gum tissue.

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

These safeguards are designed to prevent me from engaging in harmful or inappropriate behavior.

From The Wall Street Journal • Apr. 12, 2026

“In my opinion too much is taken for granted. We do not know whether all weeds in crops are harmful or whether some of them are useful,” says Dr. Briejer.

From "Silent Spring" by Rachel Carson

Vocabulary lists containing harmful

Earth Day

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Unfavorable

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