acerbate vs grieve

acerbate

verb
  • To make bitter or sour. 

  • To exasperate; to irritate. 

adj
  • Embittered; having a sour disposition or nature. 

grieve

verb
  • To cause sorrow or distress to. 

  • To submit or file a grievance (about). 

  • To feel very sad about; to mourn; to sorrow for. 

  • To experience grief. 

noun
  • A manager or steward, e.g. of a farm. 

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