regret in WordNet English dictionary

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

1. decline formally or politely
   "I regret I can't come to the party"
   regret 
   
2. express with regret
   "I regret to say that you did not gain admission to Harvard"
   regret 
   
3. feel remorse for; feel sorry for; be contrite about
   repent  regret  rue 
   
4. feel sad about the loss or absence of
   regret