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