tiara
A hairband made of metal, with a simple design and which may be embellished with gems or other ornaments. Often worn by fantasy heroines, princesses or pop idols.
Compared to a crown, the band of a tiara is usually narrow and the shape a semi-circle. Normally worn over the top of the head, in contrast to a circlet, which wraps around the forehead.
Should when possible distinguished from small clip-ons, which are jewelry or hairclips rather than a headdress.