"state of being radioactive; emissions from radioactive material or processes," 1899, from French radioactivité, coined 1898 by the Curies; see radioactive.
Entries linking to radioactivity
radioactive adj.
1898, of an atomic nucleus, "capable of spontaneous nuclear decay releasing ionizing emissions," from French radio-actif, coined by Pierre and Marie Curie from radio-, combining form of Latin radius "ray" (see radius) + actif "active" (see active). Of processes, etc., "involving or produced by radioactivity," by 1903.