(linguistics, uncountable) The reconstructed ancestor language or protolanguage of the Indo-European family of languages, which includes most European, Iranian, and Indian languages.

(anthropology, countable) A person who spoke the Proto-Indo-European language.

(linguistics, anthropology) Of or pertaining to the Proto-Indo-European language, or the people who spoke it.

The original language, or rather, cluster of dialects, from which descend the Sino-Tibetan family of languages, to include Tibeto-Burman group and the various Chinese languages; the exact phylogenetic relationships remain subject to scholarly debate.

(linguistics) The hypothetical ancestor language or protolanguage of Baltic and Slavic languages, descending from Proto-Indo-European.

(linguistics, uncountable) The hypothetical ancestor language or protolanguage of Finnic and Ugric languages. Usually written with the UPA-transcription system.

(linguistics, uncountable) The hypothetical ancestor language or protolanguage of Indo-Aryan languages, the Iranian languages, the Dardic languages and the Nuristani languages.

(anthropology, countable) A person who spoke the Proto-Indo-Iranian language.

(linguistics, anthropology) Of or pertaining to the Proto-Indo-Iranian language, or the people who spoke it.

An abjad of twenty-plus acrophonic glyphs, found in Levantine texts of the Late Bronze Age (from ca. the 15th century B.C.E.), by convention taken to last until a cut-off date of 1050 B.C.E., after which it is called Phoenician.