This study examines the lexico-semantic features of Nigerian English as deployed in Bayo Adebowale’s Lonely Days, with a view to demonstrating how language reflects cultural identity and sociolinguistic realities in Nigerian contact literature. Anchored on the theoretical insights of Adegbija (1989) Lexico – semantic Nigerianisms, the study adopts a qualitative textual analysis of selected excerpts from the novel. It explores how meaning is constructed through lexical choices and semantic processes that deviate from Standard English norms but remain contextually meaningful within the Nigerian setting. The analysis reveals that Adebowale extensively employs lexico-semantic strategies such as transfer, coinages/neologisms, semantic shift or extension and borrowing from indigenous Yoruba language. These features function not merely as linguistic deviations but as deliberate linguistic resources that encode cultural values, social structures and indigenous worldviews. Expressions such as “a man of timber and caliber,” “bad market” and “face-me-I-face-you” illustrate semantic transfer and localisation, while items like “wrapper,” “amala” and “juju” exemplify semantic extension and cultural embedding. Furthermore, the incorporation of Yoruba lexical items and expressions enhances authenticity, reinforces setting and foregrounds the oral and performative tradition inherent in African literature. The study concludes that the lexico-semantic features identified in Lonely Days substantiate the existence and legitimacy of Nigerian English as a distinct variety. They also demonstrate how Nigerian writers creatively appropriate the English language to reflect indigenous experiences, thereby expanding its expressive capacity. Ultimately, the paper affirms that lexico-semantics is central to understanding the intersection of language, culture and identity in Nigerian literary discourse. Key words: Lexico-semantics, Nigerian English, Lonely Days