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.

词汇丰富度是第二语言（L2）写作的关键维度，涵盖词汇多样性、词汇密度与词汇复杂度三大范畴。本研究以智利国际文凭（IB）7至10年级学生撰写的303篇英语作文为研究对象，分析其词汇丰富度特征。研究采用定量研究范式，借助基于语料库的测量手段，对词汇密度、多样性与复杂度进行分析，所用指标包括类符形符比（type-token ratio）、Uber指数（Uber index）以及词汇频率分析。结果表明，随着年级递增，学生的词汇多样性与复杂度均呈现显著提升趋势，9年级与10年级学生能够运用更宽泛且更具复杂度的词汇。但词汇密度整体保持相对稳定，这意味着尽管学生的词汇储备不断拓展，内容词占总词数的比例并未发生实质性变化。本研究结果既印证了IB课程在促进学生词汇发展方面的有效性，也指出了教学优化的潜在方向——尤其在提升词汇密度领域。本研究为双语教育背景下的第二语言词汇习得研究补充了实证证据，可为优化学生写作中的词汇丰富度提供教学策略参考。未来研究可拓展至多元教育场景，并探究显性词汇教学对提升词汇丰富度的作用机制。