手法を比較

	Comparative Method (Historical Linguistics)	Glottochronology (Lexical Dating)
分野	言語学	言語学
系統	Process / pipeline	Process / pipeline
提唱年	1861	1952
提唱者	Neogrammarians (Karl Brugmann, August Schleicher; building on Rasmus Rask, Jacob Grimm, Franz Bopp)	Morris Swadesh
種類	Systematic comparison of cognates to reconstruct a proto-language and establish genetic relationship	Estimation of time depth of language separation from cognate retention
原典	Campbell, L. (2013). Historical Linguistics: An Introduction (3rd ed.). Edinburgh University Press. ISBN: 9780748675593	Swadesh, M. (1955). Towards greater accuracy in lexicostatistic dating. International Journal of American Linguistics, 21(2), 121–137.
別名	Comparative Reconstruction, Comparative Linguistic Reconstruction, Method of Comparative Reconstruction	Glottochronology, Lexicostatistic Dating, Linguistic Dating
関連	4	4
概要	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.	Glottochronology is Morris Swadesh's method for estimating the time depth at which two related languages separated, derived from the proportion of basic-vocabulary cognates they still share. Building directly on lexicostatistics, it adds a crucial extra assumption — a 'glottoclock' — that basic vocabulary is lost at an approximately constant rate over time, analogous to radioactive decay. Plugging the observed cognate proportion into a logarithmic decay formula yields an estimated separation date in years. The method is historically important but has been heavily criticized, and most historical linguists today treat its dates with great caution.