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

 

radium

 noun
noun
BrE BrE//ˈreɪdiəm//
 
; NAmE NAmE//ˈreɪdiəm//
 
[uncountable](symbol Ra)
 
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a chemical element. Radium is a white radioactive metal used in the treatment of diseases such as cancer. Word Origin late 19th cent.: from Latin radius ‘ray’ + -ium.
See the Oxford Advanced American Dictionary entry: radium