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Definition of radioactivity noun from the Oxford Advanced Learner's Dictionary

radioactivity

noun
 
/ˌreɪdiəʊækˈtɪvəti/
 
/ˌreɪdiəʊækˈtɪvəti/
[uncountable]
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  1. harmful radiation that is sent out when the nuclei (= central parts) of atoms are broken up
    • the study of radioactivity
    • a rise in the level of radioactivity
    Topics Physics and chemistryc1
previously
adverb
 
 
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