Emily Dickinson Lexicon

DI'A-DEM, n. [Gr. διαδημα, from διαδεω, to gird; δια and δεω, to bind; L. diadema.]

1. Anciently, a head-band or fillet worn by kings as a badge of royalty. It was made of silk, linen or wool, and tied round the temples and forehead, the ends being tied behind and let fall on the neck. It was usually white and plain; sometimes embroidered with gold, or set with pearls and precious stones.
2. In modern usage, the mark or badge of royalty, worn on the head; a crown; and figuratively, empire; supreme power. – Gibbon.
3. A distinguished or principal ornament. A diadem of beauty. Is. xxviii.