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

Among them are an emerald-and-diamond necklace that Napoleon I gave his wife, Empress Marie-Louise, and a diadem that once belonged to the Empress Eugenie, which is dotted with nearly 2,000 diamonds.

From Barron's • Oct. 30, 2025

If you're looking at it and wondering why it seems familiar, it might be because that diadem was seen on stamps from the late Queen's reign.

From BBC • Nov. 7, 2023

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

But Russian forces managed to find the room and lifted the diadem along with 1,700 other artifacts.

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