Lexical Richness

Lexical richness is a crucial aspect of second language (L2) writing, encompassing lexical diversity, density, and sophistication. This study examines the lexical richness of 303 English compositions written by International Baccalaureate (IB) students (grades 7–10) in Chile. Using a quantitative approach, the study analyses lexical density, diversity, and sophistication through corpus-based measures, including type-token ratio, Uber index, and lexical frequency profiling. Results indicate a significant increase in lexical diversity and sophistication as students progress through grade levels, with 9th and 10th graders incorporating a broader and more sophisticated vocabulary. However, lexical density remains relatively stable, suggesting that while students expand their vocabulary, the proportion of content words to total words does not substantially change. These findings highlight the effectiveness of the IB curriculum in fostering lexical development while pointing to potential areas for instructional enhancement, particularly in promoting lexical density. The study contributes to research on L2 vocabulary acquisition in bilingual educational contexts, offering insights into pedagogical strategies for enhancing lexical richness in student writing. Future research should examine varied educational settings and investigate the role of explicit vocabulary instruction in developing lexical richness.