glottochronology

noun

the study of the rate of change occurring in the vocabularies of languages for the purpose of calculating the length of time (time depth) during which two related languages have developed independently

Wiktionary

Pronunciation: /ˌɡlɒtəʊkɹəˈnɒlədʒi/ / /ˌɡlɑːtoʊkɹəˈnɑːləd͡ʒi/

noun

Etymology: Etymology tree English glotto- Ancient Greek χρόνος (khrónos)bor. English chrono- Proto-Indo-European *leǵ- Ancient Greek λόγος (lógos) Proto-Indo-European *-h₂ Proto-Indo-European *-éh₂ Proto-Indo-European *-i-eh₂ Proto-Hellenic *-íā Ancient Greek -ῐ́ᾱ (-ĭ́ā) Ancient Greek -λογῐ́ᾱ (-logĭ́ā)bor. Latin -logialbor. French -logiebor. English -logy English chronology English glottochronology From glotto- + chronology.

The method or study in estimating the time at which a related language diverged from its common ancestor.