An apostolic bull or a Papal bull refers to a special type of patent or charter which is issued by a pope. It gets its name from the seal (bulla) that was affixed at the end to authenticate it. The Apostolic Bull is viewed as the most solemn kind of papal document. Practically speaking, an apostolic bull is an apostolic letter which has a leaden seal. The pope takes on the title 'episcopus, servus servorum Dei' in a bull. This translates as "Bishop, Servant of the Servants of God." A bull, in terms of content, is basically the format in which a papal decree appears. A bull could deal with a range of topics including excommunications, statutory decrees, Episcopal appointments, dispensations, canonizations, apostolic constitutions, and convocations.
While earlier all papal letters were referred to as bulls, nowadays a papal bull is issued only for the most formal or the most solemn of occasions such as the appointment of a bishop.
While earlier all papal letters were referred to as bulls, nowadays a papal bull is issued only for the most formal or the most solemn of occasions such as the appointment of a bishop.