irradiation vs radiation

irradiation

noun
  • An act of irradiating, or state of being irradiated. 

  • a process of sterilization whereby radiation is passed through a bag containing food, utensils, etc., to sterilize the contents. 

radiation

noun
  • The process of radiating waves or particles. 

  • The transfer of energy via radiation. 

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

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

  • Radioactive energy. 

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