pain vs regret

pain

noun
  • The condition or fact of suffering or anguish especially mental, as opposed to pleasure; torment; distress 

  • An ache or bodily suffering, or an instance of this; an unpleasant sensation, resulting from a derangement of functions, disease, or injury by violence; hurt. 

  • An annoying person or thing. 

  • Labour; effort; great care or trouble taken in doing something. 

verb
  • To feel pain; to hurt. 

  • To hurt; to put to bodily uneasiness or anguish; to afflict with uneasy sensations of any degree of intensity; to torment; to torture. 

  • To render uneasy in mind; to disquiet; to distress; to grieve. 

regret

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. 

verb
  • 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. 

  • To feel sorry about (any thing). 

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