Measuring the vocabulary load of engineering textbooks for EFL undergraduates

• EFL engineering undergraduates need to know 5000 word families to read a textbook.
• 3500 Word families are the vocabulary threshold for civil and mechanical engineering.
• The vocabulary demands of marine and biochemical engineering stretch to 8500 words.
• The EEWL includes the 729 most frequent word families beyond the BNC/COCA 2000.
• The EEWL provides 14.3 % lexical coverage of an engineering textbook.

The purpose of this research was twofold: to examine the vocabulary demands of English-medium engineering textbooks and to create an Engineering English Word List (EEWL) to cover EFL students’ lexical shortage. The researcher compiled a corpus containing 4.57 million running words of 100 college textbooks across 20 engineering subject areas from e-book databases as the source of analysis. The results demonstrate that knowing the most frequent 5000 word families plus proper nouns, apparent compounds and abbreviations would command 95% lexical coverage of an engineering textbook to ensure adequate comprehension. Civil engineering and mechanical engineering, involving 3500 word families necessary for minimally acceptable comprehension, were the least lexically demanding, while marine engineering and biochemical engineering were the most demanding in lexis, stretching to a threshold of 8500 word families. Beyond the first 2000 words, 729 of the most frequently-occurring word families in the corpus were ultimately chosen, and these covered 14.3% of the total words in the engineering textbooks. The present EEWL may provide a window to the engineering register for matriculating engineering students and may be helpful for English for science and technology teachers when preparing Engineering English teaching materials for reading and vocabulary development.