lightheartedness vs sorrow

lightheartedness

noun
  • The state of being lighthearted, joyous, cheerful, without a care. 

  • An amusement or item of a pleasant but inconsequential nature. 

sorrow

verb
  • To feel grief over; to mourn, regret. 

  • To feel or express grief. 

noun
  • (usually in plural) An instance or cause of unhappiness. 

  • unhappiness, woe 

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