The unveiling diachronic changes in interactive metadiscourse use in the academic writing of applied linguistics over 45 years

While interactive metadiscourse in academic writing has garnered considerable attention from synchronic perspectives, its diachronic investigations are relatively underexplored. This study, therefore, examines the diachronic changes in interactive metadiscourse use in the academic writing of applied linguistics spanning 45 years (1980–2024) to investigate the overall trends, categorical patterns, and use of key expressions within each category. Results indicated a fluctuating overall increase with a recent notable upward trend. Transitions and frame markers exhibited a declining tendency, whereas evidentials, code glosses, and endophoric markers have been increasingly used over the years. Most key expressions followed the diachronic categorical patterns, but several displayed distinct and significant over-time changes. These diachronic changes reflect broader transformations in disciplinary paradigm shifts, evolving academic conventions, and the impact of digital technologies on scholarly communication practices. • A fluctuating rise in the use of interactive metadiscourse from 1980 to 2024 with a recent surge from 1995 to 2024. • Shifts in metadiscourse across categories reflected disciplinary, academic, and digital transformations. • Divergent trajectories in the use of key expressions revealed nuanced diachronic dynamics.