THE IMPACT OF ENGLISH VOCABULARY PROFICIENCY ON ACADEMIC ACHIEVEMENT AND LEARNING OUTCOMES

Abstract

English vocabulary is a fundamental component of academic language proficiency because students must understand, interpret, and produce increasingly complex language across textbooks, lectures, examinations, assignments, research articles, and classroom interactions. Vocabulary knowledge encompasses not only the number of words a learner knows but also the depth of knowledge associated with those words, including meaning, grammatical behavior, collocations, word formation, and contextual use. Research on second-language vocabulary consistently indicates that lexical knowledge is closely associated with reading comprehension and broader academic performance. Schmitt et al. (2011), for example, demonstrated a strong relationship between the proportion of words known in a text and reading comprehension, emphasizing the importance of adequate lexical coverage. Academic vocabulary is also particularly important because students encounter recurring words across disciplines that are less frequent in everyday communication. Coxhead (2000) identified 570 academic word families that accounted for approximately 10% of the words in her academic corpus, demonstrating the substantial role of academic vocabulary in university-level texts. This article reviews the role of English vocabulary in academic achievement, focusing on vocabulary breadth, vocabulary depth, academic vocabulary, reading comprehension, academic writing, listening, classroom participation, examinations, and learning efficiency. The review indicates that vocabulary should not be regarded as the sole determinant of academic achievement, but as an important linguistic resource that facilitates access to academic knowledge and enables students to demonstrate their knowledge effectively.