The interaction of meaning similarity and confusability explains regularity in form-meaning mappings at and below the word level

Languages exhibit striking regularities in how meanings are mapped to word forms, yet analogous patterns at the subword level remain under-explored. This study presents a large-scale cross-linguistic analysis of regularity at and below the word level, drawing on data from over 1,900 languages. We find that while the co-expression of meanings at both levels is highly systematic, the specific meanings recurrently involved in the two levels differ. Despite these differences, regularity at and below the word level is explained by the same underlying principle: a tension between pressure for lexical compression—favoring form reuse for related meanings, thus easing learning and processing—and for lexical differentiation—favoring distinct forms to avoid confusion in context. These findings thus offer a unified account of lexical organization across the world’s languages, with subword-level form reuse emerging as a principled compromise under universal functional pressures.