Vocabulary in one of the main parts of learning English is very important because it cannot be separated in understanding the four skills of English; listening, reading, writing and speaking. There are two basic components that we must have if we want to learn English, namely vocabulary or words and grammar or sentence structure. The aim of this research is to increase student involvement in mobile�based language learning vocabulary for students at SMP Negeri 0 5 Sungai Kakap. This research uses a classroom action method which includes two cycles.
This research lasted one month with a duration of four meetings where each cycle lasted two meetings.
The findings of this research are that the use of the Duolingo application is effective in increasing student engagement in mobile-based language learning vocabulary for class VIII students, this is shown from the acquisition of the average score and the classroom situation clearly shows the improvements that occur. in the first cycle the average score was 55 compared to the increase that occurred in the second cycle the average score was 72. The improvement in the class cycle can be seen from the behavior of students who are more active during lessons. The results obtained by the researchers prove that the Duolingo application can definitely increase student engagement in mobile-based language learning vocabulary for students at SMP Negei 05 Sungai Kakap.

Keywords: Duolingo Application, English Vocabulary, Classroom Action Research