Article 14 Vienna Convention on Diplomatic Relations
1.Heads of mission are divided into three classes, namely:
(a) That of ambassadors or nuncios accredited to Heads of State, and other heads of mission of equivalent rank;
(b) That of envoys, ministers and internuncios accredited to Heads of State;
(c) That of chargés d’affaires accredited to Ministers for Foreign Affairs.
2.Except as concerns precedence and etiquette, there shall be no differentiation between heads of mission by reason of their class.
See also: Article 13 Vienna Convention on Diplomatic Relations