What is the meaning of regret?

noun

• Sadness associated with some wrong done or some disappointment.
  • usage: "he drank to drown his sorrows"; "he wrote a note expressing his regret"; "to his rue, the error cost him the game"
  • synonyms: sorrow, rue, ruefulness

verb

• Feel remorse for; feel sorry for; be contrite about.
  • synonyms: repent, rue
• Feel sad about the loss or absence of.
• Decline formally or politely.
  • usage: "I regret I can't come to the party"
• Express with regret.
  • usage: "I regret to say that you did not gain admission to Harvard"