Etiquette

noun

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.
2. The customary behavior of members of a profession, business, law, or sports team towards each other.
3. A label used to indicate that a letter is to be sent by airmail.