Duden

The Duden ( ) is a dictionary of the German language, first published by Konrad Duden in 1880. The Duden is updated regularly, with new editions appearing every four or five years. Currently it is in its 25th edition and in 12 volumes, each covering different aspects such as loanwords, etymology, pronunciation, synonyms, etc. The first of these volumes, Die deutsche Rechtschreibung (English: German Orthography), has long been the prescriptive source for the spelling of German.