alternative vs facultative

alternative

adj
  • Relating to a choice between two or more possibilities. 

  • Presenting two or more alternatives. 

  • Other; different from something else. 

  • Not traditional, outside the mainstream, underground. 

noun
  • A situation which allows a mutually exclusive choice between two or more possibilities; a choice between two or more possibilities. 

  • One of several mutually exclusive things which can be chosen. 

  • alternative rock 

  • A non-offensive word or phrase that serves as a replacement for a word deemed offensive or unacceptable, though not as a euphemism. 

  • The remaining option; something available after other possibilities have been exhausted. 

facultative

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

  • That grants permission or power to do something. 

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

  • Not obligate; optional, discretionary or elective. 

  • At which a given function is positive. 

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