Melan Rhoza Paulus. 2026. The Use of Microsoft Copilot Application to Enhance English Vocabulary Mastery Among Eleventh Grade Students of SMAN 1 Palopo (Supervised by Reski Yusrini Islamiah Y. and Andi Mangnguntungi S.).
The objective of this research was to determine whether the use of the Microsoft Copilot Application could enhance students’ English vocabulary mastery among eleventh-grade students of SMAN 1 Palopo. This research employed a quantitative method using a pre-experimental design with a one-group pre-test and post-test. The sample of this research consisted of 27 students of Class XI Pajajaran, selected through purposive sampling. The instrument used in this research was a vocabulary test administered before and after the treatment. The treatment was conducted through the Microsoft Copilot Application as a learning tool to help students identify unfamiliar vocabulary, understand word meanings, find synonyms and antonyms, and practise vocabulary in descriptive texts. The findings revealed that the students’ English vocabulary mastery improved after the implementation of the treatment. The students’ mean score increased from 53.89 in the pre-test to 80.96 in the post-test. Moreover, the result of the paired samples t-test showed a significance value (Sig. 2-tailed) of 0.000, which was lower than the significance level of 0.05 (0.000 < 0.05). Therefore, the alternative hypothesis (H₁) was accepted, while the null hypothesis (H₀) was rejected. It can be concluded that Microsoft Copilot Application significantly enhanced the English vocabulary mastery of eleventh-grade students of SMAN 1 Palopo.