Merriam-Webster's Collegiate® Dictionary, 11th Edition
REGRET
I. verb (regretted; regretting) see: greet
Date: 14th century
transitive verb
1. to mourn the loss or death of, to miss very much, to be very sorry for , intransitive verb to experience regret, regretter noun
II. noun
Date: 1590
sorrow aroused by circumstances beyond one's control or power to repair,
2. an expression of distressing emotion (as sorrow or disappointment), a note politely declining an invitation, see: sorrow regretful adjective regretfulness noun