etiquette

noun3

1. •
   The manners or decent behaviour to be observed in social or professional life; conventional decorum; the ceremonial code of polite society.

   • 20 May 2018, Hadley Freeman in The Guardian, Is Meghan Markle the American the royals have needed all along? Much shock was expressed in the British press about the Palace’s utter failure to control the Markles and the Markles’ lack of etiquette.
2. •
   The customary behavior of members of a profession, business, law, or sports team towards each other.

   • Cycling's complex etiquette contains an unwritten rule that riders in contention for a race win should not be penalised for sheer misfortune. — 2012
3. •
   A label used to indicate that a letter is to be sent by airmail.