diadem, in ancient times, the fillet of silk, wool, or linen tied about the head of a king, queen, or priest as a distinguishing mark. Later, it was a band of gold, which gave rise to the crown. In heraldry, the diadem is one of the arched bars that support the crown.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.