Abstrak
This study aims to improve students' vocabulary mastery by using domino cards. The research was conducted at SMP Negeri 10 Tarakan, with the subjects being 30 students from class VII-4. The research employed a Classroom Action Research (CAR) method. The design of this action research is collaborative, involving the English teacher as a collaborator in the classroom. This research used the Kemmis and McTaggart model, which was implemented in two cycles, with each cycle consisting of the following stages: planning, acting, observing, and reflecting. The research instruments used were an observation checklist and a vocabulary test. The results of this study indicate that there was progress in students' vocabulary mastery, which can be seen from the vocabulary test scores. In the first cycle, the students' test results did not meet the success criteria, as only 70% of the students achieved the Kriteria Ketercapaian Tujuan Pembelajaran (KKTP) or the learning outcome criteria. However, in the second cycle, 87% of the students achieved the KKTP, thus meeting the success criteria. The results from the observation checklist also show that both the teacher's and students' activities met the success criteria in every meeting. It can be concluded that the implementation of domino cards successfully improved vocabulary mastery among seventh-grade students at SMP Negeri 10 Tarakan.