Getra Leci. 2023. The effectiveness of Duolingo Application in Teaching English at SMP Kristen Rantai Damai (supervised by Resky Yusrini Islamiah Yunus and Tsamratul'aeni)
This research aims to improve students' vocabulary mastery and Grammar, using the Duolingo application which students have never found in the English learning method at school. Based on the researcher's experience by using the Duolingo application in learning English language, researcher wants to find out that whether this application is effective in improving the students' English mastery in vocabulary and grammar, and also in learning especially English learning students never used technological media as a media for learning language English. The subject of this research were seventh grade students of SMP Kristen Rantai Damai. The method of this research is quantitative method. The researcher used a pre-experimental design. To compare the students‟ score after giving a treatment and post-test, there are an increase number of scores of researchers than the pre-test. The data shows that student improve their understand and memorize English mastery. The result of the analysis showed a significant different, in the pre-test the students' mean score was 61.33 and post-test was 91.00. This is also seen in the results of the probability value is less than α (0.000 <0.05), this indicates that the alternative hypothesis (H1) is accepted, and the null hypothesis (H0) is rejected. Based on the results of the research, it was concluded that the use of Duolingo application is effective to improve vocabulary mastery at seventh grade researcher of SMP Kristen Rantai Damai.
Keyword: English, Duolingo, Vocabulary.