delusion vs illusion

delusion

noun
  • The state of being deluded or misled, or process of deluding somebody. 

  • A false belief that is resistant to confrontation with actual facts. 

  • A fixed, false belief, that will not change, despite evidence to the contrary. 

  • That which is falsely or delusively believed or propagated; false belief; error in belief. 

illusion

noun
  • The state of being deceived or misled. 

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

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

  • A magician’s trick. 

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