Coronets

In English, a coronet is a small crown consisting of ornaments fixed on a metal ring. By one definition, a coronet differs from a crown in that a coronet never has arches, and from a tiara in that a coronet completely encircles the head, while a tiara does not. By a slightly different definition, a crown is worn by an emperor, empress, king or queen; a coronet by a nobleman or lady. See also diadem.

In other languages, this distinction is not made as usually the same word for crown is used irrespective of rank (krone in German, kroon in Dutch, krona in Swedish, etc.)

The main use is now actually not on the head (indeed, many people entitled to a coronet never have one made; the same even applies to some monarchs' crowns, as in Belgium) but as a rank symbol in heraldry, adorning a coat of arms.

The word stems from the Old French coronete, a diminutive of co(u)ronne ("crown"), itself from the Latin corona (also "wreath"), from the Ancient Greek κορώνη (korōnē, "garland, wreath").

Traditionally, such headgear is – as indicated by the German equivalent Adelskrone (literally "crown of nobility") – used by nobles and by princes and princesses in their coats of arms, rather than by monarchs, for whom the word crown is customarily reserved in formal English, while many languages have no such terminological distinction. Other than a crown, a coronet shows the rank of the respective noble. Hence, in German and Scandinavian languages there is also the term Rangkrone.

For equivalents, both physical and emblematic, in other languages and cultures, see under crown (headgear).

In the United Kingdom, a peer wears his or her coronet on one occasion only: for a royal coronation, when it is worn along with coronation robes, equally standardised as a luxurious uniform.

In the peerages of the United Kingdom, the design of a coronet shows the rank of its owner, as in German, French and various other heraldic traditions. Dukes were the first individuals authorised to wear coronets. Marquesses acquired coronets in the 15th century, earls in the 16th and viscounts and barons in the 17th. Until the barons received coronets in 1661, the coronets of earls, marquesses and dukes were engraved while those of viscounts were plain. After 1661, however, viscomital coronets became engraved, while baronial coronets were plain. Coronets may not bear any precious or semi-precious stones.

...
Wikipedia