The study aims to investigate vocabulary demands in academic textbooks for ELT majors, identifying the most frequent word list for preservice teachers and variations in lexical needs across sub-areas. For the purposes, the study compiled a corpus comprising approximately 1.6 million tokens from twelve university textbooks in the integral dimensions of ELT: language acquisition and teaching methodology. By analyzing the lexical coverage of the ELT textbook corpus against the twenty-five 1,000 word-family list from the British National Corpus and Corpus of Contemporary American English (BNC/COCA), the study assessed the lexical load of ELT textbooks and developed an essential vocabulary list. Findings revealed that achieving a 95% lexical coverage in ELT textbooks necessitates mastery of the top 4,000 word families, including proper nouns, interjections, transparent compounds, abbreviations, and glossary terms. To attain 98% coverage, however, ELT students require an 11,000-word family vocabulary. Further analyses show that textbooks in language acquisition demand a higher lexical requirement compared to those in teaching methodology. By applying a set of criteria for widespread use and pedagogical relevance, the study identified 513 word families beyond the initial 2,000 levels on the BNC/COCA, constituting 9.36% of the ELT textbooks. The study suggests practical pedagogical implications.
