What is the reconstructed ancestor of the Indo-European languages called?

The reconstructed ancestor of the Indo-European languages is called Proto-Indo-European. Linguists use this name for the hypothetical common ancestor of languages as diverse as English, Spanish, Russian, Greek, Persian, Hindi, and Bengali.

Proto-Indo-European was never directly recorded in writing. Instead, scholars reconstruct it by comparing documented descendant languages and identifying regular similarities in vocabulary, grammar, and sound changes. For example, English father, Latin pater, and Sanskrit pitár- reflect patterns that point back to an older shared form.

The reconstruction became a major project in the 19th century, helping establish the comparative method and systematic sound laws. Linguists conventionally mark reconstructed words with an asterisk because they are scholarly proposals rather than quotations from surviving documents. The language is often abbreviated PIE.

Proto-Indo-European should not be confused with Proto-Germanic, Proto-Slavic, or Proto-Romance. Those were later ancestral stages of particular branches: Germanic includes English and German, Slavic includes Russian and Polish, and Romance developed from varieties of Latin. The exact homeland and date of PIE remain subjects of scholarly debate.