A family of languages (including most of the languages spoken in Europe, India, and Iran) descended from a common tongue spoken in the third millennium B.C. by an agricultural people originating in southeastern Europe. Branches of Indo-European (IE) include Indo-Iranian (Sanskrit and the Iranian languages), Greek, Italic (Latin and related languages), Celtic, Germanic (which includes English), Armenian, Balto-Slavic, Albanian, Anatolian, and Tocharian. See also: Grimm's Law.
Etymology:
The theory that languages as diverse as Sanskrit, Greek, Celtic, Gothic, and Persian had a common ancestor was proposed by Sir William Jones in an address to the Asiatick Society on Feb. 2, 1786.Examples and Observations:
- "The ancestor of all the IE languages is called Proto-Indo-European, or PIE for short. . . .
"Since no documents in reconstructed PIE are preserved or can reasonably hope to be found, the structure of this hypothesized language will always be somewhat controversial."
(Benjamin W. Fortson, IV, Indo-European Language and Culture. Wiley, 2009) - "The languages of Europe and those of Northern India, Iran, and part of Western Asia belong to a group known as the Indo-European Languages. They probably originated from a common language-speaking group about 4000 BC and then split up as various subgroups migrated. English shares many words with these Indo-European languages, though some of the similarities may be masked by sound changes. The word moon, for example, appears in recognizable forms in languages as different as German (Mond), Latin (mensis, meaning 'month'), Lithuanian (menuo), and Greek (meis, meaning 'month'). The word yoke is recognizable in German (Joch), Latin (iugum), Russian (igo), and Sanskrit (yugam)."
(Seth Lerer, Inventing English: A Portable History of the Language. Columbia Univ. Press, 2007)

