This study examines the roles and significance of affixation in Idoma word formation with the aim to identify how words are affixed in Idoma language. The paper employs both primary and secondary data sources. Primary data were collected through participant observation, audio recordings, oral interviews, and note-taking from 40 native speakers of Idoma language from Otukpo Local Government Area, consisting of language experts, educators, and cultural custodian. The theoretical framework adapted in this study was the item and arrangement theory. The theory is suitable for analyzing the sequential arrangement of morphemes and their morphological relevance. The findings revealed that affixes in Idoma are actively involved in generating new lexical items and modifying existing ones.

They perform key roles such as agentive formation (e.g., verbs to nouns abstract nominalization, causative formation, possession marking and semantic specification. Also, the study identifies three major types of affixes in Idoma: prefixes, suffixes, and infixes. Prefixes are the most dominant and productive, particularly the “o-” class, which derives agentive nouns from verbs, and the “i-” class, which forms abstract nouns from verbs and adjectives. Other prefixes such as “bi-,” “i-,” and “ya-” are also observed to derive verbs from adjectives, often with causative meanings. Suffixes, though less productive, are clearly attested and include forms such as “-m,” “-nu,” “-le,” “-ncha,”

and “-ha,” which express possession, specification, abstraction, and other semantic extensions. Moreso, the study confirms the existence of infixation, particularly the insertion of the vowel “o” within roots, which contributes to progressive aspect marking, nominalization, and intensification. The study concludes that derivational affixation is a fundamental and productive feature of Idoma morphology, playing a crucial role in word formation and meaning extension.