illusion vs semblance

illusion

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

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

  • A magician’s trick. 

  • The state of being deceived or misled. 

semblance

noun
  • the way something looks; appearance; form 

  • likeness, similarity; the quality of being similar. 

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