The Effects of Vocabulary Breadth and Depth on Junior High School Students’ Reading Comprehension

This study investigated the effects of breadth and depth of vocabulary knowledge, both partially and simultaneously, on the reading comprehension of junior high school students. A quantitative associative research design was employed using multiple linear regression analysis. The sample consisted of 31 second-year students at UPT SPF SMP Negeri 48 Makassar, selected through cluster random sampling. Data were collected using the Vocabulary Levels Test (VLT) to measure breadth of vocabulary knowledge, the Word Associates Test (WAT) to measure depth of vocabulary knowledge, and a multiple-choice reading comprehension test. The data were analyzed using descriptive statistics and multiple linear regression analysis, consisting of the partial test (t-test) and the simultaneous test (F-test). The findings revealed that breadth of vocabulary knowledge had a significant partial effect on reading comprehension (t = 8.028, Sig. = 0.000, Beta = 0.700), and depth of vocabulary knowledge also had a significant partial effect on reading comprehension (t = 3.482, Sig. = 0.002, Beta = 0.303). Furthermore, breadth and depth of vocabulary knowledge simultaneously had a significant effect on reading comprehension (F = 199.181, Sig. = 0.000), with a coefficient of determination (R²) of 0.934, indicating that 93.4% of the variance in students’ reading comprehension could be explained by both variables, while the remaining 6.6% was influenced by other factors outside this study. These findings suggest that English teachers should design vocabulary instruction that balances the expansion of students’ vocabulary size with the deepening of their understanding of word meaning, usage, and context in order to improve students’ reading comprehension.