radiation vs radioactivity

radiation

noun
  • Radioactive energy. 

  • The transfer of energy via radiation. 

  • The shooting forth of anything from a point or surface, like diverging rays of light. 

  • The process of radiating waves or particles. 

  • A rapid diversification of an ancestral species into many new forms. 

radioactivity

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

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

How often have the words radiation and radioactivity occurred in a corpus of books? (source: Google Ngram Viewer )