illusion vs mirage

illusion

noun
  • A magician’s trick. 

  • A misapprehension; a belief in something that is in fact not true. 

  • Anything that seems to be something that it is not. 

  • The state of being deceived or misled. 

mirage

noun
  • An illusion. 

  • An optical phenomenon in which light is refracted through a layer of hot air close to the ground, often giving the illusion of a body of water. 

verb
  • To cause to appear as or like a mirage. 

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