Measuring the effect of receptive and productive vocabulary size on foreign language skills

Vocabulary knowledge and usage play a significant role in developing English language skills. Determining students' vocabulary levels can be an effective way to track the development of their language skills and predict their test performance. Therefore, this study examined the relationship between receptive and productive vocabulary knowledge and English language skills (reading, writing, listening, speaking, and use of English) of 306 Turkish university students who are A1, A2, and B1-level EFL learners. Vocabulary knowledge was measured using the New Vocabulary Levels Test (NVLT) and the Vocabulary Levels Test-Productive (VLTP), while language skills were assessed through an English Proficiency Exam (EPE) and a speaking exam. The results revealed significant positive correlations between receptive and productive vocabulary knowledge, particularly at higher proficiency levels. Receptive vocabulary was found to be a much stronger predictor of language skills, especially for reading, listening, and use of English, than productive vocabulary which predicted performance in use of English. However, the impact of both vocabulary tests was more pronounced at higher proficiency levels. While vocabulary levels show some predictive power on specific language skills, their influence is limited overall. These findings suggest a nuanced relationship between vocabulary and language proficiency, offering valuable insights for educators and researchers.