harmful

adjective

harm·​ful ˈhärm-fəl 

: of a kind likely to be damaging : injurious

harmful chemicals

harmfully

ˈhärm-fə-lē 

adverb

harmfulness noun

Synonyms of harmful

• detrimental
• damaging
• dangerous
• adverse
• bad

Examples of harmful in a Sentence

DDT has been proven to be extremely harmful to the environment.

Recent Examples on the Web

Removing barriers The new facility seeks to provide more dignity for clients and remove barriers that keep victims from separating themselves from harmful environments, Mortensen said. —Elliot Mann, Twin Cities, 19 Apr. 2026

This method allows harmful bacteria to survive and grow, and additional cooking cannot eliminate these bacteria. —Lisa Cericola, Southern Living, 19 Apr. 2026

Police said nothing harmful was found. —ABC News, 19 Apr. 2026

This can leave a harmful reside. —Cody Godwin, USA Today, 19 Apr. 2026

Word History

First Known Use

14th century, in the meaning defined above

Rhymes for harmful

• armful

Kids Definition

harmful

adjective

harm·​ful ˈhärm-fəl 

: causing damage : injurious

harmfully

-fə-lē 

adverb

harmfulness noun

Legal Definition

harmful

adjective

harm·​ful

: of a kind likely to cause harm

harmfully adverb

harmfulness noun