alternative vs obligation

alternative

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

  • 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 

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

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. 

obligation

noun
  • A social, legal, or moral requirement, duty, contract, or promise that compels someone to follow or avoid a particular course of action. 

  • A course of action imposed by society, law, or conscience by which someone is bound or restricted. 

  • The act of binding oneself by a social, legal, or moral tie to someone. 

  • A legal agreement stipulating a specified action or forbearance by a party to the agreement; the document containing such agreement. 

  • The fact of being obliged to, that is, grateful for, something. 

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