Origins of the word "steward" in transportation are reflected in the term "chief steward" as used in maritime transport terminology. The term purser and chief steward are often used interchangeably describing personnel with similar duties among seafaring occupations. This lingual derivation results from the international British maritime tradition (i.e. chief mate) dating back to the 14th century and the civilian United States Merchant Marine on which US aviation is somewhat modeled. Due to international conventions and agreements, in which all ships' personnel who sail internationally are similarly documented by their respective countries, the U.S. Merchant Marine assigns such duties to the chief steward in the overall rank and command structure of which pursers are not positionally represented or rostered.