Command: respond

Usage: respond

After you receive a tell, even from an invisible ainur, you can use the
'respond' command to initiate a reply.  You will be prompted for the text
you would like to reply. 

For example:
  Someone tells you: hi!
  > respond
  You will tell Someone:
      ^^ at this prompt you can enter your reply text

See also:    tell,  tellhist