This article discusses about the use of an android mobile application, Duolingo, to improve students of junior high school vocabulary mastery. Purpose of study: The study aims to find out how is the process of the students acquire vocabulary through playing the game? and, can the application improve the student’s vocabulary mastery? Method: It is a case study involving 30 students as participants. Questionnaires and vocabulary Test were given to the students after playing the game for several times. Result: It is found that most of the students are excited and enjoying playing the game. Gamification is the most favorite features according to them. They acquire many vocabularies after playing the game based on the vocabulary Test result. Conclusion: It is concluded that Duolingo, an android application, is increasing the student’s motivation in learning English as well as improves their vocabulary mastery.
Keywords: Duolingo, English vocabulary, Vocabulary Mastery, game in teaching, vocabulary acquisition
