periodicity vs recursion

periodicity

noun
  • The quality of being periodic; tendency to recur at regular intervals. 

  • Recurrence of a woman's periods; menstruation. 

  • The quality of a function with a repeated set of values at regular intervals. 

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 periodicity and recursion occurred in a corpus of books? (source: Google Ngram Viewer )