facultative vs nondiscretionary

facultative

adj
  • That grants permission or power to do something. 

  • Able to perform a particular life function, or to live generally, in more than one way. 

  • Of or relating to faculty, especially to mental faculty. 

  • Not obligate; optional, discretionary or elective. 

  • At which a given function is positive. 

nondiscretionary

adj
  • Not discretionary; thus, frequently, mandatory 

  • Of or pertaining to non-discretionary spending 

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