zucchetto

A small round skullcap worn by Christian clergymen. Typically associated with clergymen of the Catholic Church, though is also worn in the Syriac Orthodox Church and some Protestant churches. It is customary for the zuchetto to be worn under the biretta and mitre.

In Catholicism, the pope has a white zuchetto, and cardinals have a red zuchetto. It can also be seen in purple and black, typically by bishops and priests/deacons respectively.

Also known as a pilelous, its official name, but also sometimes designated as a berettino, calotte, subbiretum, submitrale, or soli-deo.