originally, an officer in medieval Europe charged with carrying messages to and from the commanders of opposing armies; in modern times, a professional authority on armorial history and genealogy. In the 12th century heralds formally announced and conducted tournaments, including the proclamation of each joust and the name of each combatant. To carry out these duties it was essential that the herald be familiar with the family derivation and be able to recognize the arms of local nobles on sight. In the 14th century heralds began to serve nobles on a more permanent basis and became associated with their names and houses. In the late 14th century the authority of the heralds was expanded. By the early 15th century the principal herald (king of arms) had become a commissioner for nobilitas minor (“minor nobility”), a term now embracing all the nobility ranking below the peerage and including baronets, Scottish barons, lairds, knights, esquires, and gentlemen. When the crown ceased to grant arms directly, its powers were delegated to the heralds as commissioners, with authority to issue letters patent. In the 16th and 17th centuries heralds were called upon to carry out visitations at which men bearing arms were required to present proof of their right to do so.

Heralds served thoughout Europe, not only the kings and principal magnates but also the great orders of knighthood such as those of the Garter and the Golden Fleece.

Heralds in both England and Scotland record arms and pedigrees, grant arms, take part in high ceremonial, and settle matters of precedence. There are, however, certain significant differences between Scottish and English heralds, as there are between Scottish and English heraldry. The Scottish heralds are still “familiar daylie servitors” of the crown. The Lord Lyon King of Arms is a great officer of state, the supreme officer of honour and counsel to the sovereign in all matters of armorial, genealogical, and ceremonial import. Within his power is everything that pertains to chiefship of name and arms and to changes of name by all bearers of arms. As Controller of Her Majesty's Messengers at Arms, he is the head of the whole executive department of the law in Scotland. English kings of arms have less extensive powers, derived from the Earl Marshal, do not exercise judicial power, and cannot change names. Both English and Scottish heralds still wear the tabard, an official cape or coat with the royal arms of the United Kingdom emblazoned on it.