What is "lexicostatistics"

n. Statistical estimation of the degree of linguistic divergence between two languages, based on the proportion of cognates.

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

Lexicostatistics is an approach to comparative linguistics that involves quantitative comparison of lexical cognates. Lexicostatistics is related to the comparative method but does not reconstruct a proto-language. 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; other applications of it may not share the assumption of a constant rate of change for basic lexical items.

The term "lexicostatistics" is misleading in that mathematical equations are used but not statistics. Other features of a language may be used other than the lexicon, though this is unusual. Whereas the comparative method used shared identified innovations to determine sub-groups, lexicostatistics does not identify these. The latter is a distance based method but the comparative method considers language characters directly. The lexicostatistics method is a simple and fast technique relative to the comparative method but has limitations that are discussed below. It can be validated by cross-checking the trees produced by both methods.