recurrence vs recursion

recurrence

noun
  • The instance of recurring; frequent occurrence. 

  • A return of symptoms as part of the natural progress of a disease. 

  • Recourse. 

  • Return or reversion to a certain state. 

recursion

noun
  • The act of recurring. 

  • The act of defining an object (usually a function) in terms of that object itself. 

  • The invocation of a procedure from within itself. 

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