radiation vs spreading

radiation

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

  • The transfer of energy via radiation. 

  • The process of radiating waves or particles. 

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

  • Radioactive energy. 

spreading

noun
  • The act by which something is spread. 

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