Maria Yosefina Danggo Pengarang ELISNA HUAN Dosen Pembimbing 2 Alexander Home Kabelen Dosen Pembimbing 1 Alexander Home Kabelen Penguji 1 Elisna Huan Penguji 2 Johnson W. Haan Ketua Penguji

This thesis is entitled: 'The Effectiveness of Using Crossword Puzzle Game in Improving Vocabulary Mastery of the Eighth Students of SMPN 16 Satarmese, Manggarai in the Academic 2023/2024’. The problem of this research is: What extent does crossword puzzle game vocabulary mastery of the eighth-grade students of SMPN 16 Satarmese, Manggarai in the academic year 2023/2024? This research aims to know the effectiveness of using crossword puzzle games to improve the mastery of English vocabulary of the eighth-grade students of SMPN 16 Satarmese, Manggarai in the academic year 2023/2024. The method used in this study was the experimental method. This research was conducted in SMPN 16 Satarmese, Manggarai in December 2023. There were 44 students of SMPN 16 Satarmese taken as of this study. The researcher used a random sampling technique. This sample was divided into two groups: the experimental group which consisted of 22 students and the control group which consisted of 22 students. The instrument used to collect data was a multiple choice test which consisted of 30 items. In collecting the data, the researcher used pretest, treatment, and post-test as the data collection procedures then followed by analyzing the data by using the t-test formula. The result of data analysis shows that using of crossword puzzle game can improve the vocabulary of eighth-grade students of SMPN 16 Satarmese, Manggarai in the academic year 2023/2024 because the result of the statistical calculation indicated that the value of the t-test was 2,89 and the value of df (degree of freedom) 42 at the level of significance 5% was 2,10. Since the t-test was higher than the t-table value thus, the alternative hypothesis (H1), was accepted and the null hypothesis (H0) was rejected. It means that the use of crossword puzzle games can improve vocabulary mastery of the eighth-grade students of SMPN 16 Satarmese, Manggarai in the academic year 2023/2024. Key Words: Crossword Puzzle Game, Improving and Vocabulary.