Crown
A crown is a type of headdress worn by a monarch. They are usually worn when they are crowned or at important occasions. Also, crowns are now used as a symbol of the monarchy. They are also won by beauty pageant winners.
"Crown" is also a synonym for prize or reward. Crowns are awarded or won at contests. Beauty contests award crowns to the winning participant, for example. Couples chosen the King and Queen at a dance also receive crowns.
Diadem
A diadem is a type of crown, an ornamental headband worn by monarchs and others as a badge of royalty.
Crown Media
Imperial State Crown of the United Kingdom
Imperial Crown of Kingdom of Sicily (Crown of Constance of Aragon, Cathedral of Palermo).
Imperial Crown of Russia, 2012 replica
Vajracarya's Ritual Crown, Ancient Nepal
The Seobongchong Golden Crown of Ancient Silla, which is 339th National Treasure of South Korea. It is basically following the standard type of Silla's Crown. It was excavated by Swedish Crown Prince Gustaf VI Adolf in 1926.
Crown of King of Persis Ardakhshir II, 1st century BC.
Crown of Darius the Great, c. 500 BC.