If you have ever sent an email using Gmail with only text in the subject line, you have seen the prompt asking if you want to send the email without text in the body. This is to make sure that you have not forgotten to insert the body text as most emails have body text. If you want to avoid that prompt when sending emails that only have text in the subject line all you have to do is add "EOM" or "(EOM)" which stands for end of message.
"I often send messages where the subject is the entire message (e.g. "Want to grab lunch at 12:30?"), and Gmail would always prompt me to add in body text.
Now, however, you can add "EOM" or "(EOM)" at the end of the subject line (short for End Of Message), and Gmail will silently send the message without the unnecessary prompt."