coronet

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.