constituent vs facultative

constituent

adj
  • constitutive or constituting; (politics) authorized to make a constitution 

  • being a part, or component of a whole 

noun
  • A resident of an area represented by an elected official, particularly in relation to that official. 

  • A part, or component of a whole 

  • A person or thing which constitutes, determines, or constructs 

  • A functional element of a phrase or clause 

  • A voter who supports a (political) candidate; a supporter of a cause. 

  • One who appoints another to act for him as attorney in fact 

facultative

adj
  • Not obligate; optional, discretionary or elective. 

  • 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. 

  • At which a given function is positive. 

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