Exploring Factors that Affect English Vocabulary Development among Pakistani University Students: A Focus on Receptive and Productive Knowledge Inam Ullah Dept. of English language and Literature The Graduate School Kwangwoon University This dissertation investigates the development and acquisition of receptive and productive English vocabulary among Pakistani university students, exploring the discrepancy between these two aspects across varying word frequency levels, proficiency levels, and the effect of specific lexical factors. The findings suggest that the high frequency words are easier to learn than the low- frequency words. This pattern suggests a stronger inclination towards comprehension rather than production among the students. Furthermore, significant differences were observed in vocabulary acquisition between high and low proficiency groups, emphasizing the role of learners’ language proficiency in shaping language skills. The factorial ANOVA results showed that frequency levels effect the receptive nad productive scores without showing any interaction effect. It means that frequency levels effect the test scores independently and are not bound with the test types and so do the test types. Further analysis showed that the proficiency levels have an interaction effect between the test types and both test type and proficiency levels effect the receptive and productive scores. Multiple regression analysis among the receptive and productive vocabulary scores was preformed to investigate an in-depth examination of lexical factors such as word frequency, word length, orthographic spread, sum bigram frequency; orthographic uniqueness point, orthographic neighborhood density, and OLD 20 M etc. highlighted their substantial impact on L2 vocabulary learning. Particularly, orthographic spread was the significant predictor of receptive vocabulary development while word length and raw frequency were found significant predictors of productive vocabulary acquisition. The empirical data and findings of this research are quite novel and have never been explored before. Prior research primarily focused only on one direction of the English vocabulary (receptive vocabulary) as it is quite easy to explore, whereas the other dimension of the vocabulary knowledge (productive vocabulary) has not been explored yet. Keeping the fact in mind; and to learn the distinction between receptive and productive knowledge, how it develops, how long does it take to develop, and which factors significantly impact the growth of receptive or productive vocabulary knowledge this research was much needed. Despite its contributions, the study faced limitations like lack of funding and period which may impact the generalizability of the findings. Future research directions include a deeper investigation into the cognitive processes behind vocabulary acquisition, longitudinal studies, and the development of tailored language interventions for Pakistani university students. Additionally, comparative studies across different cultural contexts are recommended to enhance the understanding of L2 vocabulary acquisition universally.