Which scientist coined the term 'radioactivity'?

Marie Curie coined the term “radioactivity” to describe the emission of radiation by certain substances.

Curie introduced the concept and the French term radioactivité during her investigations of uranium compounds in 1898. She measured radiation with great precision and showed that the phenomenon depended on the amount of uranium present, not on the compound’s chemical form. This led her to argue that radioactivity was an atomic property.

Her research grew out of Henri Becquerel’s 1896 discovery that uranium salts emitted penetrating rays. Curie expanded the work by testing many minerals and found that pitchblende was much more active than uranium alone. With Pierre Curie, she used that clue to search for new elements, announcing polonium in July 1898 and radium in December.

Becquerel discovered the phenomenon, but he did not coin its modern name. Pierre Curie was Marie’s close collaborator, so some historical accounts credit the couple jointly with popularizing the term; Marie is the standard individual answer because she introduced it in her scientific work.