advisor vs referee

advisor

noun
  • One who offers advice. 

  • A xiangqi piece, that is moved one point diagonally and confined within the palace. 

referee

noun
  • A person who writes a letter of reference or provides a reference by phone call for someone. US English: reference. 

  • A person who settles a dispute. 

  • An expert who judges the manuscript of an article or book to decide if it should be published. 

  • An umpire or judge; an official who makes sure the rules are followed during a game. 

verb
  • To act as a referee. 

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