Abstrak
This study aimed to determine the effect of the Teams Games Tournament (TGT) learning model on the vocabulary mastery of the eighth-grade students at MTs Negeri Tarakan. A quantitative approach was employed using a pre-experimental method with a one-group pretest posttest design. The sample consisted of 32 students from class VIII-A, selected through purposive sampling based on preliminary study from questionnaire and interview indicating low English vocabulary mastery. The research instrument was a short-answer test covering four types of vocabulary: concrete nouns, lexical verbs, descriptive adjectives, and adverbs of manner. Data were analyzed using a paired sample t-test, which revealed a significance value (p) of 0.0000.05, indicating a significant difference between pretest and posttest scores. Thus, the null hypothesis (Ho) was rejected, and the alternative hypothesis (Ha) was accepted. Furthermore, the N-Gain calculation showed an improvement in students' vocabulary mastery with a moderate significance level of 0.4. This indicates a considerable increase in vocabulary mastery after the treatment, although further improvements were still possible to achieve optimal learning outcomes. Qualitative findings also showed enhanced active participation, learning motivation, and contextual understanding of vocabulary through group discussions and tournament activities. Based on these results, it can be concluded that the TGT model was effective in improving students' vocabulary mastery and fosters a collaborative as well as competitive learning experience. The study recommends broader implementation of this model with longer treatment periods.