Definition of "etiquette"

etiquette

/ˈɛt.ɪˌkɛt/

noun
countable and uncountable, plural etiquettes
1. The forms required by a good upbringing, or prescribed by authority, to be observed in social or official life; observance of the proprieties of rank and occasion; conventional decorum; ceremonial code of polite society.
  Quotations
  Much shock was expressed in the British press about the Palace’s utter failure to control the Markles and the Markles’ lack of etiquette.
  20 May 2018, Hadley Freeman in The Guardian, Is Meghan Markle the American the royals have needed all along?
  Whenever Root would put his elbows on the table or clatter his dishes or commit any other breach of etiquette, the Professor would gently correct him.
  2003, Yoko Ogawa, The Housekeeper and the Professor
2. The customary behavior of members of a profession, business, law, or sports team towards each other.
  Quotations
  Cycling's complex etiquette contains an unwritten rule that riders in contention for a race win should not be penalised for sheer misfortune.
  2012 July 15, Richard Williams, Tour de France 2012: Carpet tacks cannot force Bradley Wiggins off track‎, Guardian Unlimited
3. A label used to indicate that a letter is to be sent by airmail.