from
Bouvier's Law Dictionary, Revised 6th Ed (1856)
DIPLOMATIC AGENTS. This name has been given to public officers, who have
been commissioned, according to law, to superintend and transact the affairs
of the government which has employed them, in a foreign country. Vattel,
liv. 4, c. 5.
2. These agents are of divers orders, and are known by different
denominations. Those of the first order are almost the perfect
representatives of the government by which they are commissioned; they are
legates, nuncios, internuncios, ambassadors, ministers, plenipotentiaries.
Those of the second order do not so fully represent their government; they
are envoys, residents, ministers, charges d'affaires, and consuls. Vide
these several words.