“Mayday” is a code word used internationally as a radio distress signal for a life-threatening emergency. It is derived from the French phrase venez m’aider, meaning “come help me.” “Mayday” should be repeated three times, followed by the vessel’s call sign, also repeated three times. “Mayday” and the call sign should then be stated again, followed by details about the emergency and position of the craft. What code word can be used for situations that are urgent but not life-threatening?
Source: The Free Dictionary