In situations like
- One of my colleague message me saying, I'm not able to join this week lunch
- One of the speaker message me saying, I'm not able to join the conference this time
Is it appropriate to
"it's a sad news" or
"Sad to hear that"? I think "Sad" is for more serious situations like "accident", "Funeral" etc. but in this kind of situation what is the appropriate way to express the feeling?