APOSTOLIC INTERNUNCIO. — The term internuntius is used in the briefs of Leo X to designate an envoy who exercises the office of ambassador until the sovereign has sent the proper ambassador: a kind of interim ambassador. An apostolic internuncio was also called one who deputized for the nuncio in his absence and until his arrival.
At present, however, an apostolic internuncio means a prelate, normally a titular archbishop, who is sent by the Roman pontiff as his representative, with a permanent appointment and diplomatic character, to the head of a State (Note of the Secretariat of State, 8 May 1916, Fontes CIC, VIII, no. 6457, p. 487). The apostolic internuncio differs from the nuncio because he is not, as the latter is, accorded the rank of ambassador, but that of minister plenipotentiary.
This applies solely to ceremonial prerogatives; his functions, however, are identical to those of the apostolic nuncio.