Primarily a suffix used in compound words for types of headwear (e.g., 学帽, 制帽). Can also appear as a standalone noun in some contexts, but this is less common.
See also: 帽子
Wear a school cap.
This hat is a memento of my father.
From Middle Chinese 帽 (mawH, “hat”). The kanji is used as a suffix in Japanese compounds for headwear.
bare-headed; uncovered
ordinary cap; field cap; garrison cap
putting on a hat; wearing a hat
ceremonial hat
red hat