The purposes of this research was to find out whether using anagram technique is effective or not in teaching vocabulary mastery and to find out the effect of anagram technique in teaching vocabulary mastery to the eighth grade students of SMPN 5 Sungai Kunyit. This research employed a quantitative method, specifically a pre�experimental design with a one-group pretest-posttest design. The subject in this research were eighth-grade students, totaling 32 individuals, comprising 18 male students and 14 female students at SMPN 5 Sungai Kunyit. In this research, the measurement technique was employed to collect data through essay tests. Both pre-test and post-test assessments were administered to
gather data from the students. The collected data underwent analysis using descriptive statistics with SPSS for Windows version 16.0. Data distribution was considered, and given its normalcy, a paired sample test analysis was employed to
test hypotheses. Additionally, Cohen's effect size was utilized to evaluate the impact of using the Anagram technique in teaching vocabulary mastery.
The research findings indicated the effectiveness of the Anagram Technique in teaching vocabulary mastery at the eighth grade students of SMPN 5 Sungai Kunyit. This was evidenced by the differences observed in the mean scores between the pre-test (64.63) and post-test (88.94), signifying a positive change after the treatment. The standard deviation (SD) of the pre-test (8.36) was lower than that of the post-test (6.72), indicating successful implementation of the treatment. Furthermore, the paired sample t-test in SPSS 16.0 yielded a significance score (Sig.) of 0.000, with an alpha-value of 0.05. As the Sig. (2-tailed) was lower than the alpha-value (0.000 < 0.05), the alternative hypothesis (Ha) was accepted, and the null hypothesis (Ho) was rejected. The effect size, based on Cohen's effect, was determined to be 1.61, signifying a strong effect of the Anagram Technique in teaching vocabulary mastery.

Keywords: Effectiveness, Anagram Technique, Vocabulary Mastery