mortar-board

The square academic cap, very commonly called a mortarboard cap, is an item of academic headgear consisting of a horizontal square board fixed upon a skull-cap, with a tassel attached to the centre. In the UK and the U.S., it is commonly referred to informally in conjunction with an academic gown worn as a cap and gown. It is also often termed a square or trencher in the UK and Australia. In the U.S., it is usually referred to more generically as a mortarboard, or simply cap.