From Side Notes to Structure: The Development of By the Way and Incidentally as Discourse Markers

Abstract

This study explores the grammaticalization and pragmatic specialization of by the way and incidentally as discourse markers in English, focusing on their role in managing digression and mitigating face-threatening acts. While both expressions originally denoted concrete meanings — spatial for by the way and incidental for incidentally — they have undergone significant functional shifts to become strategic tools for discourse management. Through corpus-based analysis of COCA and BNC, this study demonstrates that by the way and incidentally exhibit clear functional divergence across register and gender. By the way predominantly occurs in informal and spoken contexts, facilitating non-intrusive topic shifts and maintaining conversational solidarity. In contrast, incidentally appears more frequently in formal and written settings, functioning as a relevance marker that frames supplementary information with structured politeness. These findings contribute to a deeper understanding of how grammaticalization, politeness strategies, and social variation interact in the development of discourse markers. They highlight that the evolution of by the way and incidentally is shaped not only by semantic change but also by their capacity to mitigate face-threatening acts and to adapt to diverse communicative demands across different contexts.