Resumen: This paper considers the morphophonological variants found in the non-head position of Spanish productive compound patterns. In the literature it has been noted that compounds resort to both I- and O-ending stems and words (even inflected ones) to spell-out compound non-heads. The study takes a nanosyntactic approach to compound syntax and examines the functional structure of the main classes of Spanish compounds. The goal of the analysis is to show that the functional structures of compounds determine to some extent which spell-outs are chosen in lexical innovations within the schemas, and also to address the issue of why certain allomorphs never appear in a given context while others seem to compete for lexical insertion. Research was conducted using a self-compiled sample of 1250 compounds extracted from contemporary Spanish written corpora. The results provide empirical support for syntacticist approaches to compounding, in that the proposed functional structures capture the predominantly compositional semantics of compounding, and also because traditional “linking vowels” are reconsidered to be the stable and systematic spell-outs for relational categories inside compounds. Idioma: Inglés DOI: 10.3390/languages7020105 Año: 2022 Publicado en: Languages 7, 105 (2022), 22 ISSN: 2226-471X Factor impacto CITESCORE: 1.1 - Arts and Humanities (Q1) - Social Sciences (Q3)