diffusion vs radiation

diffusion

noun
  • The scattering of light by reflection from a rough surface, or by passage through a translucent medium. 

  • The gradual spread and adoption of goods or services. 

  • Exchange of airborne media between regions in space in an apparently random motion of a small scale. 

  • The spread of cultural or linguistic practices, or social institutions, in one or more communities. 

  • The movement of water vapor from regions of high concentration (high water vapor pressure) toward regions of lower concentration. 

  • The intermingling of the molecules of a fluid due to random thermal agitation. 

  • The act of diffusing or dispersing something, or the property of being diffused or dispersed; dispersion. 

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. 

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