circlet

noun

1. A small circle.
2. A ring (typically of gold or silver) worn as an ornament on the head.

   “He wore in addition to his leathern trappings and jewelled ornaments a great circlet of gold about his brow in the exact centre of which was set an immense stone, the exact counterpart of that which I had seen upon the breast of the little old man at the atmosphere plant nearly twenty years before.”

3. A crown without arches or a covering.

   “Her faire lockes in rich circlet be enrold.”

4. A round body; an orb.

   “Fairest of stars […] that crown'st the smiling morn / With thy bright circlet.”