On the Complexity and Typology of Inflectional Morphological Systems

TL;DR

This paper investigates the complexity of inflectional morphological systems across languages, revealing a trade-off between paradigm size and irregularity, measured through entropy and estimated via variational methods.

Contribution

It introduces a novel quantitative methodology to measure morphological irregularity and demonstrates a universal trade-off across 31 diverse languages.

Findings

Large paradigms tend to be highly irregular or large in size, but not both.

Entropy-based irregularity measure effectively captures paradigm complexity.

Empirical evidence supports the trade-off hypothesis across multiple language families.

Abstract

We quantify the linguistic complexity of different languages' morphological systems. We verify that there is an empirical trade-off between paradigm size and irregularity: a language's inflectional paradigms may be either large in size or highly irregular, but never both. Our methodology measures paradigm irregularity as the entropy of the surface realization of a paradigm -- how hard it is to jointly predict all the surface forms of a paradigm. We estimate this by a variational approximation. Our measurements are taken on large morphological paradigms from 31 typologically diverse languages.