radioactivity

Meanings

1. 1
   noun

   Spontaneous emission of ionizing radiation as a consequence of a nuclear reaction, or directly from the breakdown of an unstable nucleus.

   Today, no one would intentionally smear radioactive materials on their face, but in 1933, the dangers of radioactivity were not yet fully understood.

2. 2
   noun

   the spontaneous emission of a stream of particles or electromagnetic rays in nuclear decay

3. 3
   noun

   The radiation so emitted; including gamma rays, alpha particles, neutrons, electrons, positrons, etc.

From radioactive + -ity or radio- + activity.

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