Vocabulary is one of the main components of a language and is a necessity if you want to communicate. Vocabulary is a series of words used to form a sentence. In this case, the more vocabulary is mastered by students, the easier it is
for students to make sentences and communicate. Learning English, especially in memorizing vocabulary, is a tedious activity for students. Therefore, the used of media in learning vocabulary is very necessary to improve student understanding. There are several media that can be applied, one of which is a flash card. Flash card are media that are easy to apply and support effective vocabulary teaching.
Therefore, the researcher aims to determine the effectiveness of using flash card in teaching English vocabulary by conducting pre-experimental research and making SMP Negeri 1 Subah the research location and taking a sample with a total population of 77 Class 8 students, while the sample used is 25 students. The data collection process used a pre-test and post-test using multiple-choice, totaling 15 questions with data analysis using SPSS version 29. The results of this research found that the use of flash card media in the English learning process was considered effective because it had a strong influence based on the data obtained where the average score on the pre-test was 44.2 and on the post-test was 70.84. It can be seen that the average post-test score is higher than the pre-test average
score. This is proven again from the analysis of the results of the "paired sample test" using SPSS with Sig. (2-tailed) is 0.000 < 0.05. So H0 is rejected and H1 is accepted. Based on the results of measuring the effect size on the Cohen Point Estimate value of 1.967 > 1.00, it can be concluded from the research data above that flashcard media has a strong or quite large influence on students. So it can be
seen that there are differences in standard deviation and average values between the pre-test and post-test. So it can be concluded that the effectiveness of using flashcard media in teaching English vocabulary, especially to grade 8 students at SMP Negeri 1 Subah shows a strong or effective influence.

Keywords: Effectiveness, Flash Card and English Vocabulary.