<![CDATA[Basic English vocabulary mastery is the primary foundation for elementary school students to develop more complex language skills. However, foreign language learning for young learners often faces obstacles due to the limitations of concrete and contextual learning media. This study aims to measure the effectiveness of using serial picture stories on the basic English vocabulary mastery of adjectives among fifth-grade elementary school students. The research method applied was a quantitative experiment with a Nonequivalent Control Group Design. The research population included all 67 fifth-grade students of SDN Dayeuhluhur CBM Sukabumi, with samples selected using a total sampling technique divided into an experimental class (27 students) and a control class (30 students). Data collection was carried out using 15 item essay test instrument that had been tested for validity and reliability through pre-test and post-test stages. Data analysis techniques utilized descriptive and non-parametric inferential statistics with the Mann-Whitney U test via the IBM SPSS Statistics program because the data was not normally distributed. The results showed that the mean post-test score of the experimental class (85.59) increased significantly by 17.23 from the pre-test score (68.41), while the control class only increased by 5.17 from the pre-test score (72.87) to the post-test score (78.10). The hypothesis testing results revealed an Asymp. Sig. (2-tailed) value of 0.031 < 0.05, meaning H0 was rejected and H1 was accepted. Therefore, it can be concluded that the use of serial picture stories is significantly effective in improving the basic English vocabulary mastery of elementary school students.]]>
