Abstract:
Vocabulary mastery plays a fundamental role in English language learning, enabling students to comprehend texts and communicate effectively. Many senior high school EFL students struggle to identify and interpret nouns, verbs, and adjectives in analytical exposition texts, a pattern observed among eleventh-grade students where instruction relied heavily on the drilling method, limiting contextual vocabulary learning. This study was conducted because game-based vocabulary studies rarely examine grammatical categories separately, and little research has integrated a traditional Indonesian game with a structured vocabulary tool at the senior high school level. This study investigated the effectiveness of the Modified "ABC Lima Dasar" Game integrated with a Vocabulary Matrix in improving vocabulary mastery across categories, compared with the drilling method used in the control group. A quasi-experimental nonequivalent control group design was employed with 36 eleventh-grade students from two intact classes at a state senior high school in Ciamis Regency, West Java, Indonesia, divided into experimental group receiving the treatment and a control group taught through drilling. Data were collected using a 13-item multiple-choice vocabulary test administered as pre-test and post-test, analyzed through descriptive statistics, the Shapiro-Wilk test, the Mann-Whitney U test, and rank biserial correlation. The experimental group's mean score increased from 68.37 to 79.05, while the control group's mean score decreased from 67.49 to 64.08. A significant difference was found between groups (U = 78.000, Z = −2.684, p = 0.007), with a large effect size (r = 0.519). Verb mastery improved most (+0.84), followed by nouns (+0.45), while adjectives declined slightly (−0.05). These findings confirm that the treatment is more effective than drilling, and adjectives require additional support. Future research should extend the treatment and examine retention through a delayed post-test.
