dream vs illusion

dream

noun
  • A visionary scheme; a wild conceit; an idle fancy. 

  • Imaginary events seen in the mind while sleeping. 

  • A hope or wish. 

verb
  • To hope, to wish. 

  • To see imaginary events in one's mind while sleeping. 

  • To envision as an imaginary experience (usually when asleep). 

  • To consider the possibility (of). 

  • To daydream. 

adj
  • Ideal; perfect. 

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. 

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