The square academic cap, graduate cap, cap, mortarboard (because of its similarity in appearance to the mortarboard used by brickmasons to hold mortar) or Oxford cap is an item of academic dress consisting of a horizontal square board fixed upon a skull-cap, with a tassel attached to the centre. In the UK and the US, it is commonly referred to informally in conjunction with an academic gown as a "cap and gown". It is also sometimes termed a square, trencher, or corner-cap. The adjective academical is also used. The cap, together with the gown and sometimes a hood, now form the customary uniform of a university graduate in many parts of the world, following a British model. Origins The mortarboard may have developed from the biretta, a similar-looking hat worn by Roman Catholic clergy. The biretta itself may have been a development of the Roman pileus quadratus, a type of skullcap with superposed square and tump (meaning small mound). A reinvention of this type of cap is known as the Bishop Andrewes cap. The Italian biretta is a word derived from the Medieval Latin birretum from the Late Latin birrus "large hooded cloak", which is perhaps of Gaulish origin, or from Ancient Greek πυρρός pyrrhos "flame-colored, yellow". Tassel United Kingdom In the UK, the tassel is shorter and is gathered at the button at the centre of the board. The U.S. style is slightly longer, gathered at a cord attached to the button. At the University of Cambridge, undergraduates by ancient convention used to cut their tassels very short so that the tassel does not extend beyond the edge of the board. After they graduated, they wore the square cap with the tassel at the normal length. This convention has now fallen into disuse; few people now wear headgear with academic dress at any time and undergraduates in particular have no need to wear the cap. United States The American Council on Education (ACE) code states that "The tassel should be black or the colour appropriate to the subject," and makes an exception only for the gold tassel. The gold metallic tassel is reserved for those entitled to wear the doctoral gown, as is the use of velvet for headwear. Only one tassel is worn at a time. For schools where the graduation regalia is rented or borrowed by the student, the tassel might be a part of the rental