radiation vs radiation therapy

radiation

noun
  • 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. 

  • Radioactive energy. 

radiation therapy

noun
  • The use of ionizing radiation to treat disease, especially cancer. 

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