Geiriadur Prifysgol Cymru is the first standard historical Welsh dictionary, broadly comparable in method and scope with The Oxford English Dictionary , but midway in format between that dictionary and the Shorter Oxford English Dictionary . This vocabulary is defined in Welsh, but English equivalents are also given.
Detailed attention is given to variant forms, common collocations, and etymology.
The work is based upon a collection of some two million citation slips, amassed by voluntary readers as well as members of the Dictionary staff and still being added to. A reading program was established in 1921 at the National Library of Wales with a small team of salaried staff and the Rev. J. Bodvan Anwyl as Secretary who organized a host of voluntary readers. The Dictionary is the direct responsibility of the Board of Celtic Studies, and is located in purpose-built accommodation together with the Centre for Advanced Welsh and Celtic Studies in the University's new building at the National Library of Wales , where access is freely given to the unparalleled collection of Welsh books and manuscripts. The building stands on the boundary between the National Library and the campus of the University of Wales, Aberystwyth . There are eight members on the editorial staff and a part-time typist.