Mayday is the spoken radio signal that life is in immediate danger. Send a mayday, a mayday call, mayday mayday mayday.
It is said three times so that it cannot be mistaken for part of a sentence, and it outranks every other transmission on the frequency. Pan-pan is the next level down and means urgent but not life-threatening. Mayday is used by aircraft and ships worldwide regardless of language. Note that it has nothing to do with May Day the holiday, and everything to do with French.
1nounmaydayThe spoken radio signal that life is in immediate danger.
“The pilot sent out a mayday when both engines failed over the sea.”
mayday is a distress signal.
French m'aider means help me, from venez m'aider, come and help me. A British radio officer chose it in 1923 because it was clear over poor radio and would be understood by both British and French crews.
French
m'aider
English, today
mayday
Built from
From the distress signal mayday, from French m'aider, short for Venez m'aider! (“Come to help me!”). The term was conceived in the early 1920s by Frederick Stanley Mockford, officer-in-charge of radio at Croydon Airport in England. He had been asked to think of a word that would indicate distress and would easily be understood by all pilots and ground staff in an emergency. Since much of the air traffic at the time was between Croydon and Le Bourget Airport in Paris, he proposed the term "mayday," the phonetic equivalent of the French m'aider.
Etymology from Wiktionary, CC BY-SA