Proto-Indo-European Language

The Proto-Indo-European language (PIE) is the reconstructed common ancestor of the Indo-European languages, spoken by the Proto-Indo-Europeans. PIE was the first proposed proto-language to be widely accepted by linguists. Far more work has gone into reconstructing it than any other proto-language, and it is by far the most well-understood of all proto-languages at its time depth. During the 1800s, in fact, the vast majority of linguistic work was devoted to reconstruction of Proto-Indo-European or of daughter proto-languages such as Proto-Germanic, and most of the current techniques of historical linguistics (e.g. the comparative method and the method of internal reconstruction) were developed as a specific result.

Scholars estimate that PIE may have been spoken as a single language (before divergence began) around 3700 BC, though estimates by different authorities can vary by more than a millennium. The most popular hypothesis for the origin and spread of the language is the Kurgan hypothesis, which postulates an origin in the Pontic-Caspian steppe of Eastern Europe.

In modern times the existence of PIE was first postulated in the 18th century by Sir William Jones, who observed the similarities between Sanskrit, Ancient Greek, and Latin. By the early 1900s, well-defined descriptions of PIE had been developed that are still accepted today (with some refinements). The largest developments of the 20th century have been the discovery of Anatolian and Tocharian languages and the acceptance of the laryngeal theory. The Anatolian languages have also spurred a major re-evaluation of theories concerning the development of various shared Indo-European language features and the extent to which these features were present in PIE itself.

PIE is thought to have had a complex system of morphology that included inflections (suffixing of roots, as in who, whom, whose), and ablaut (vowel alterations, as in sing, sang, sung). Nouns used a sophisticated system of declension and verbs used a similarly sophisticated system of conjugation.

Relationships to other language families, including the Uralic languages, have been proposed but remain controversial.

There is no written evidence of Proto-Indo-European, so all knowledge of the language is derived by reconstruction from later languages using linguistic techniques such as the comparative method and the method of internal reconstruction.