Lexical Diversity, Density, and Word Frequency in CEFR A2 ELT Coursebook Reading Texts in Turkish Higher Education: A Corpus-Based Comparative Analysis of Three Coursebooks

Coursebooks remain a dominant source of lexical input in ELT, yet CEFR labels are often treated as proxies for lexical suitability without empirical verification. This study applies corpus-based analysis to compare the lexical characteristics of A2-level reading texts in three widely used ELT coursebookewas (Language Hub, Empower, and The Big Picture). Reading passages exceeding 50 words were compiled into three sub-corpora and analyzed across lexical diversity (TTR and MLTD), lexical density, and frequency/coverage patterns (NGSL vs. off list). Results show that surface diversity (TTR) is broadly similar across books (? 53%–55%), but length-sensitive diversity (MLTD) and text-level peaks reveal non-equivalent lexical variety across materials. Lexical density averages cluster within a moderate band (M = 50.71–52.76), yet within-book distributions include substantial…