Duden

The Duden is updated regularly with new editions appearing every four or five years. , it is in its 29th edition. It is printed as twelve volumes, with each volume covering different aspects of the German language such as loanwords, etymology, pronunciation, synonyms, etc.
The first of these volumes, '''' (English: The German orthography), has long been the prescriptive source for Standard High German spelling. The Duden has become the most widely used language resource of the Standard High German language, stating the rules regarding grammar, spelling and use of Standard High German language. In Austria, the Österreichisches Wörterbuch takes that role. Provided by Wikipedia
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