based on custom rather than documentation; "an unwritten law"; "rites...so ancient that they well might have had their unwritten origins in Aurignacian times"- J.L.T.C.Spence
a courteous expression (by word or deed) of esteem or regard; "his deference to her wishes was very flattering"; "be sure to give my respects to the dean"
courteous regard for people's feelings; "in deference to your wishes"; "out of respect for his privacy"