Other forms: SOSS
When someone piloting a boat or a plane desperately needs help, they can send an SOS. This distress signal, recognized around the world, conveys the urgency of the situation.
A Morse code SOS is transmitted by sending three dots, three dashes, and three dots in rapid succession. It was developed for maritime use, so sailors could clearly signal for help. Contrary to popular belief, SOS is not an acronym: although you can think of it as "save our ship" or "save our souls," those don't explain its origin. Instead, the letters were chosen because they were "easy to transmit and difficult to mistake" from other Morse code characters.