Comparative Method (Historical Linguistics)

The comparative method is the foundational technique of historical linguistics for demonstrating that languages are genetically related and for reconstructing their unattested common ancestor. By systematically comparing cognate words across related languages and uncovering the regular, recurring sound correspondences between them — exemplified by Grimm's Law in Germanic — analysts reconstruct the forms of the proto-language and the sound changes that produced each daughter, and on that basis build the family tree. It is a qualitative, evidence-driven method distinct from the generic logic of cross-case comparison: here the 'comparison' is of linguistic forms governed by the regularity of sound change.