Proto-Indo-European 
noun [mass noun]
The lost language from which all Indo-European languages derive. See Indo-European.The standard estimate for the time depth of the Indo-European parent language, Proto-Indo-European, is perhaps 6,000 years BP....
- This was the basis of the reconstruction of the ancient and hypothetical language, Proto-Indo-European, from which we believe are derived most European tongues, and many spoken in Western and Central Asia.
- All are presumed to have descended from a single common ancestor language known as Proto-Indo-European.
adjective
Relating to Proto-Indo-European.A significant number of animals were probably brought, first by the Proto-Indo-European peoples, into northern Iberia during the fifth millennium B.P., and second by the Roman invasions ca. 2300 B.P....
- ‘Sagacity’ in English print in 1548 was originally the ability to track or hunt, in Proto-Indo-European cultures.
- Whatever the truth, the mystery and magic of our Proto-Indo-European heritage has continued to fascinate me and many scholars in the field.