Disciplinary variation in grammatical complexity in university science textbooks in Hong Kong

This study investigates disciplinary variation in grammatical complexity in university textbooks across four disciplines in scientific domains (i.e., chemistry, computing mathematics, physics, and biology). A corpus was built by collecting science textbooks from a Hong Kong university, where an English Medium Instruction (EMI) policy was implemented. The frequencies of 11 clausal and phrasal complexity features (Biber et al., 2011) were included in our analysis. The corpus was tagged by the Biber Tagger, and then individual features were extracted and counted. The Kruskal-Wallis Test and post-hoc analysis were run to explore the differences in the frequencies of the 11 features across the textbooks in the four disciplines. The findings show significant differences in the frequencies of the grammatical complexity features with varied effect sizes. Substantial disciplinary variations were found in both phrasal features (i.e., appositive noun phrases and premodifying nouns) and clausal features (i.e., passive voices and finite relative clauses). A functional interpretation is also provided to explain the communicative purposes fulfilled by grammatical features. This study offers valuable insights for designing tailored pedagogical materials to develop students’ scientific literacy in this HK university or similar educational contexts. © 2025 The Authors.