diadem

American  

[dahy-uh-dem] / ˈdaɪ əˌdɛm /

noun

1. a crown.

2. a cloth headband, sometimes adorned with jewels, formerly worn by monarchs in Asia Minor and other parts of the East.

3. royal dignity or authority.

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verb (used with object)

1. to adorn with or as if with a diadem; crown.

diadem British  

/ ˈdaɪəˌdɛm /

noun

1. a royal crown, esp a light jewelled circlet

2. royal dignity or power

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verb

1. (tr) to adorn or crown with or as with a diadem

Etymology

Origin of diadem

1250–1300; Middle English diademe (< Anglo-French ) < Latin diadēma < Greek diádēma fillet, band, equivalent to diadē- (verbid stem of diadeîn to bind round + -ma noun suffix

Explanation

A diadem is a crown, or something on a crown. If you’ve just won the Miss America pageant, reach up your hand — that’s right — that rhinestone encrusted circlet on your head? That’s a diadem. While diadem is a straightforward word meaning "crown," it can also refer to the jewels or other ornaments on a crown. It also sounds like diamond, which is handy for remembering the meaning, because a crown might well have diamonds on it. Or, the diadem could be the diamond on the crown. Technically, you could have a diadem on a diadem, but it would be confusing to say it that way. It comes from the Greek diadema, which was cloth tied around the head to signify royalty. Not as nice as diamonds though, really!

Example Sentences

Also stolen was a diadem that once belonged to the Empress Eugenie, which has nearly 2,000 diamonds; and a necklace that once belonged to Marie-Amelie, the last queen of France.

From Barron's • Oct. 20, 2025

Almost 1 meter in diameter, the vessel entombed a woman in her late 20s with a shining silver diadem on her forehead.

From Science Magazine • Oct. 4, 2023

This new statue in York has a traditional design - with the Queen in the robes of the Order of the Garter and wearing the George IV diadem.

From BBC • Nov. 9, 2022

Museum officials tried to hide the diadem and other objects in a secret basement.

From Washington Post • Nov. 4, 2022

“Professor Flitwick says the diadem vanished with Ravenclaw herself. People have looked, but,” she appealed to her fellow Ravenclaws, “nobody’s ever found a trace of it, have they?”

From "Harry Potter and the Deathly Hallows" by J.K. Rowling