friction vs variance

friction

noun
  • Conflict, as between persons having dissimilar ideas or interests; clash. 

  • The rubbing of one object or surface against another. 

  • A force that resists the relative motion or tendency to such motion of two bodies in contact. 

  • (Second Sino-Japanese War) Conflict, as between the Communists and non-Hanjian Kuomintang forces. 

variance

noun
  • The state of differing or being in conflict. 

  • A discrepancy between two legal documents. 

  • A departure from a cause of action originally in a complaint. 

  • An official permit to do something that is ordinarily forbidden by regulations. 

  • The act of varying or the state of being variable. 

  • The number of degrees of freedom in a system. 

  • Covariance and contravariance generally. 

  • A difference between what is expected and what is observed; deviation. 

  • The second central moment in probability. 

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