Reporting on a study of 79 languages (see appendix B), I argue that (morpho)syntactic structure plays a crucial role in two observed asymmetries: (a) in nouns, number-driven root suppletion is common while case-driven root suppletion is virtually unattested, and (b) in contrast to lexical nouns, pronouns commonly supplete for both number and case. I propose that the structural difference between lexical nouns and pronouns, combined with locality effects as proposed in Distributed Morphology (DM; Halle and Marantz 1993), accounts for the two asymmetries. This raises the question whether these asymmetries can be captured in frameworks that deny that hierarchical syntactic structure plays a role in the morphology, such as word-and-paradigm approaches (e.g., Anderson 1992, Stump 2001).
Suppletion refers to the situation where a single lexical item is associated with two phonologically unrelated forms, and the choice of form depends on the morphosyntactic context (see Corbett 2007...