the study of linguistic divergence between two languages, based on changes in a list of common vocabulary terms and the sharing of common root words (see also glottochronology).

a statistical technique used in glottochronology; used to estimate how long ago different languages evolved from a common source language

A manner of determining subgroups of language families used mainly with lesser known languages that uses the percentage of cognates in the core vocabulary of two languages to determine their likely relationship.

a method of core vocabulary comparison between related languages

Lexicostatistics is an approach to comparative linguistics that involves quantative comparison of cognates. It is to be distinguished from glottochronology, which attempts to use lexicostatistical methods to estimate the length of time since two or more languages diverged from a common earlier proto-language. This is merely one application of lexicostatistics, however, and other applications of it may not share the assumption of a constant rate of change for basic lexical items.