sad vs unhappy

sad

adj
  • Causing sorrow; lamentable. 

  • Soggy (to refer to pastries). 

  • Of colours: dark, deep; later, sombre, dull. 

  • Appearing sorrowful. 

  • Feeling sorrow; sorrowful, mournful. 

  • Poor in quality, bad; shameful, deplorable; later, regrettable, poor. 

  • Unfashionable; socially inadequate or undesirable. 

unhappy

adj
  • Not happy; sad. 

  • Not satisfied; unsatisfied. 

noun
  • An individual who is not happy. 

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