Having rich and complex vocabulary is a crucial component that contributes to the quality of writing for academic purposes. However, use of academic vocabulary can be challenging for adolescent L2 writers who are developing their academic language proficiency. Thus, understanding lexical needs of adolescent L2 students in composing academic essays is pivotal in supporting this population in their endeavor to become proficient academic writers. This study investigates the lexical features of adolescent L2 students’ text-based analytical essays and analyzes the extent to which lexical density, lexical diversity, and lexical sophistication predict the quality of their writing. Computational tools Coh-Metrix and VocabProfiler were used to obtain quantitative measures of lexical density, diversity, and sophistication. The results of the study indicate that the essays (n = 70), on average, have (1) low lexical density, (2) more repetition of words indicating less diversity compared to grade-level estimates, and (3) a higher percentage of basic words and lower percentage of academic words. 44 % of the AWL words in the essays come from the source text and prompt. The results of multiple hierarchical regression indicate that the use of academic vocabulary is a predictor of writing quality. The study has important pedagogical implications for classroom practice at secondary school.

拥有丰富而复杂的词汇表是提高学术写作质量的重要组成部分。但是，使用学术词汇对于正在发展其学术语言能力的L2青春期作家可能具有挑战性。因此，了解青少年二年级学生在撰写学术论文时的词汇需求对于支持该群体成为熟练的学术作家的努力至关重要。这项研究调查了青少年L2学生基于文本的分析性论文的词法特征，并分析了词法密度，词法多样性和词法复杂性在多大程度上预测了他们的写作质量。计算工具Coh-Metrix和VocabProfiler用于获得词汇密度，多样性和复杂性的定量度量。研究结果表明，平均而言，论文（n = 70）具有（1）较低的词汇密度，（2）与等级级别的估计相比，单词的重复次数更多，表明多样性较少，（3）更高的百分比基本单词的百分比和学术单词的百分比较低。论文中44％的AWL单词来自原文和提示。多元层次回归的结果表明，学术词汇的使用是写作质量的预测指标。该研究对中学课堂教学具有重要的教学意义。论文中44％的AWL单词来自原文和提示。多元层次回归的结果表明，学术词汇的使用是写作质量的预测指标。该研究对中学课堂教学具有重要的教学意义。论文中44％的AWL单词来自原文和提示。多元层次回归的结果表明，学术词汇的使用是写作质量的预测指标。该研究对中学课堂教学具有重要的教学意义。