The hood was originally a functional garment, worn to shield the head from the elements. In the English tradition, it has developed to an often bright and decorative garment worn only on special occasions. It is also worn by clergy and lay readers of the Anglican Communion in choir dress, over the surplice, and it is common in cathedrals, churches, and chapels for the choirmaster and/or members of the choir to wear an academic hood to which they are entitled during services, over their cassock and surplice, although only for the choir offices (Morning and Evening Prayer) and not for the Eucharist.
Hoods comprise two basic patterns: full shape or simple shape. The traditional full-shape hood consists of a cape, cowl, and liripipe, as is used at Cambridge. At Oxford, the bachelors' and masters' hoods use simple hoods that have lost their cape and retain only the cowl and liripipe. Some universities only have a cape and cowl and no liripipe; these are referred to as the Aberdeen shape. Various other universities have different shapes and patterns of hoods, in some cases corresponding to the pattern current at the ancient universities at the time when they were founded, and in others representing a completely new design.
The colour and lining of hoods in academic dress represents the rank and/or faculty of the wearer. In many Commonwealth universities bachelors wear hoods edged or lined with white rabbit fur, while masters wear hoods lined with coloured silk (originally ermine or other expensive fur). Doctors' hoods are normally made of scarlet cloth and lined with coloured silk. Faculty colours were introduced by the University of London and many universities followed suit.
The hood is nearly always worn with a gown though there are some exceptions such as Oxford doctors who do not wear a hood with their festal robes (though this regulation is often ignored at graduation ceremonies at other universities when Oxford doctors are sitting in the faculty).
The neckband of the hood usually has a loop of which original function is to hook onto the button of a cassock. Since many do not wear cassocks for graduation, the loop is sometimes hooked onto a shirt button instead. However, since the hood is rather heavy this has a tendency to pull the lightweight shirt upwards. The correct way to wear the hood is to allow the neckband to naturally hook itself onto the collar under the tie which secures the hood in place. Sometimes, the hood is worn too forward and down being hooked onto the jacket button or pinned which causes the hood to sit badly and more be likely slip down the shoulders like a shawl.