dEu

Deu is the ISO 639-3 three-letter code for the German language. It is used in language tagging, linguistic databases, and metadata to identify German unambiguously. In ISO 639-2, German has two codes: ger for bibliographic purposes and deu for terminology; in practice many systems align with the 639-3 standard, which uses deu for German.

The German language itself is a West Germanic language of the Indo-European family. It is the official or national language of Germany, Austria, and Liechtenstein, one of the official languages of Switzerland, Luxembourg, and Belgium, and is spoken by communities across Europe and beyond. There are about 90 million native speakers and over 100–120 million total speakers. German exists in Standard German (Hochdeutsch) as a standard variety, with numerous regional dialects grouped into Low German, Central German, and Upper German. It has a rich literary and scholarly tradition and a complex morphology, with noun capitalization, four grammatical cases, three grammatical genders, separable and inseparable prefixes, and strong and weak verb conjugations. The German orthography uses the Latin script with umlauts (ä, ö, ü) and the ß ligature.

As a language code, deu is used in many technical contexts, including language tagging in software, databases, and digital archives, and is part of international efforts to classify and organize linguistic resources.