A corpus-driven, diachronic analysis of recurrent word combinations across academic disciplines

Given the significance of lexical bundles as recurrent word combinations in academic research writing, diachronic analyses of these linguistic expressions in writing research articles (ras) may offer important insights into how they may have changed in frequency, structure and function across disciplines over time. To address possible diachronic and disciplinary variations in lexical bundles in academic writing over the past fifty years, we drew on a corpus of 4,363,206 words from highly ranked academic research journals in three disciplines. Frequency analyses revealed a relatively small decrease in the number of word combinations across the disciplines over time. Although very few shared lexical bundles recurred in the academic disciplines over time, they were used more frequently across the three time periods than in the disciplines. Structurally, lexical bundles were generally comprised of noun and prepositional phrases with of -phrase fragments. Functionally, text-orientated and participant-orientated bundles were the most and the least frequent expressions, respectively, across the disciplines over time. However, we observe a shift from research-orientated to text-orientated bundles in chemistry and psychology since 1985. The findings showed a strong relationship between structural types and discourse functions of lexical bundles. The findings suggest that lexical bundles are not only unstable but also susceptible to variation across disciplines.