Investigating Valency in Causative Verb Derivational Mechanisms: The Case of the Oromo Language

This paper examines verb derivation in Oromo, focusing on how causative morphological suffixes such as -s-, -sis-, and -sisiis- alter verb valency and argument structure. The study investigates whether verbs derived through these causative morphemes behave differently from non-derived verbs, especially in subsequent valency-changing operations. It also explores the interaction of causative morphology with inchoative and ideophonic roots. A qualitative descriptive methodology was employed, combining primary data from native Oromo speakers with secondary sources such as grammars and linguistic corpora. Verbs were categorized by inherent valency and analyzed using a morphosyntactic framework grounded in valency theory and derivational morphology. Findings reveal that the suffix –s– in CS1 pattern marks direct causation and agentivization, and increases valency by introducing an agentive subject. The suffix –si(i)s– in CS2 pattern encodes indirect causation, adding intermediate agents and expanding argument roles. The suffix –sisiis– in CS3 pattern represents causative stacking, where the subject functions as an effector, producing multi-agent constructions. The study reinterprets geminated forms like -ess- as composites of inchoative and causative morphemes, shaped by morphophonemic processes such as palatalization and vowel harmony. The research proposes a valency code system ([1A] through [5E]) to map argument expansion across derivational layers. Comparative insights from other Cushitic languages highlight both shared phonological processes and divergent morphological strategies. This study contributes to morphosyntactic typology by clarifying the functional distinctions among causative suffixes, demonstrating how morphological stacking reshapes clause architecture, and offering a framework for analyzing valency manipulation in Afroasiatic languages.