crown prince vs heir

crown prince

noun
  • A person expected to inherit or take over an enterprise or undertaking once its current manager retires or dies. 

  • A person designated and raised to become the next emperor. 

  • A person designated and raised to become the next king. 

heir

noun
  • One who inherits, or has been designated to inherit, a hereditary title or office. 

  • A successor in a role, representing continuity with the predecessor. 

  • Someone who inherits, or is designated to inherit, the property of another. 

verb
  • To inherit. 

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