The hairstyle where hair is twisted and coiled into a circular shape on the head is a bun.
To make a bun, hair is generally pulled back, twisted or braided, and wrapped around itself in a circular coil. It may sit on the crown, at the back of the head, or near the nape of the neck. Hair ties, bobby pins, hair sticks, clips, nets, and donut-shaped inserts can help secure or add volume to the style.
Buns appear in many cultural and historical hairstyles. Traditional forms include the Japanese mage, the Chinese ji, and the Sikh joora, while modern versions include ballet buns, messy buns, space buns, and braided buns. Their practical appeal is simple: they keep long hair controlled and away from the face.
“Updo” is a broader category for hair arranged upward or away from the shoulders, so a bun can be an updo but not every updo is a bun. A chignon is a related style, usually a low bun or coil at the nape, while a topknot specifically emphasizes placement on top of the head.