How do scholars reconstruct the Proto-Germanic language without written records?

Scholars reconstruct Proto-Germanic, the unrecorded parent language of the Germanic branch, primarily through the comparative method. Because no written records of this language exist, linguists analyze related words and grammatical structures across descendant languages—such as Gothic, Old Norse, Old English, and Old High German—to deduce the ancestral forms.12

Reconstructed forms are marked with an asterisk to indicate their hypothetical nature. The process relies on the principle of regular sound change, where scholars identify systematic correspondences between sounds in different languages. For instance, by comparing words for "guest" across various early Germanic languages, linguists reconstruct the Proto-Germanic form *gastiz.13

These reconstructions are more than mere formulas; they provide insight into the language's phonology and structure. Occasionally, external evidence, such as early loanwords in other languages like Finnish, provides confirmation for these deductions. By applying these methods, linguists can also trace the relationship between Germanic and other branches of the Indo-European family, such as Celtic, Italic, and Greek.13