one of the most influential German (German language)-language scholars before Jacob Grimm. His grammars, dictionary, and works on style helped to standardize the language.

He engaged in private research from 1761 to 1787, when he became principal librarian to the elector of Saxony at Dresden, a post he retained to the end of his life.

Adelung's Versuch eines vollständigen Grammatisch-kritischen Wörterbuches der hochdeutschen Mundart (1774–86; “Attempt at a Complete Grammatical-Critical Dictionary of the High German Dialect”) revealed an intimate knowledge of the history of dialects basic to modern German. At the time of his death, he was still at work on Mithridates, oder allgemeine Sprachenkunde, 3 vol. (1806–17; “Mithridates, or General Linguistics”), in which he affirmed the relation of Sanskrit and the major European languages and also collected the Lord's Prayer in some 500 languages and dialects.