Oxford Advanced American Dictionary

Definition of harmful adjective from the Oxford Advanced Learner's Dictionary

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harmful

adjective
harmful pronunciation English ˈhɑːmfl harmful pronunciation American ˈhɑːrmfl
(rather formal)
 
causing damage or injury to somebody/something, especially to a person's health or to the environment
the harmful effects of alcoholthe sun's harmful ultra-violet raysMany household products are potentially harmful.harmful to somebody/something Fruit juices can be harmful to children's teeth.harmfully
harmfully pronunciation English ˈhɑːmfəli harmfully pronunciation American ˈhɑːrmfəli
adverb harmfulness
harmfulness pronunciation English ˈhɑːmflnəs harmfulness pronunciation American ˈhɑːrmflnəs
noun [uncountable]