grieve vs regret

grieve

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

  • To submit or file a grievance (about). 

  • To cause sorrow or distress to. 

  • To experience grief. 

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

regret

verb
  • To feel sorry about (any thing). 

  • To feel sorry about (a thing that has or has not happened), afterthink: to wish that a thing had not happened, that something else had happened instead. 

noun
  • Emotional pain on account of something done or experienced in the past, with a wish that it had been different; a looking back with dissatisfaction or with longing. 

  • The amount of avoidable loss that results from choosing the wrong action. 

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