Ordbog over det norrøne prosasprog. The Dictionary of Old Norse Prose (ONP) is an online dictionary containing over 50,000 words. The headwords are in Old Norse, while the definitions are in Danish and/or English. The dictionary covers medieval Old Norse material found in prose texts from the oldest written documents to early modern times (Old Icelandic 1150-1540 and Old Norwegian 1150-1370). After the publication of the first four volumes of an intended thirteen volume printed edition, a decision was made to change the format of the dictionary to a digital edition available online. Published by the University of Copenhagen, the project is ongoing as of 2020 with new words added regularly. The dictionary is searchable in a number of ways: by headword, text, manuscript, type of word, and numerous others.