The Indo-European languages constitute a vast family of several hundred related languages and dialects, including most major languages of Europe, the Iranian plateau, and the northern Indian subcontinent. This family, which encompasses branches such as Germanic (e.g., English), Romance (e.g., Spanish), Slavic (e.g., Russian), and Indo-Aryan (e.g., Hindi), is theorized to have descended from a single prehistoric ancestor known as Proto-Indo-European (PIE). Linguists establish these genetic relationships through the comparative method, which identifies systematic similarities in vocabulary, grammar, and sound systems, thereby revealing deep historical connections between cultures that have been geographically and politically separate for millennia.