YOHANA AMALIATY SUNYA Pengarang ELISNA HUAN Dosen Pembimbing 1 DEWI I N BILI BORA Dosen Pembimbing 2 Dewi I N Bili Bora Penguji 1 Elisna Huan, S. Pd., M.Hum Ketua Penguji Novriani R. Manafe, S.S. M.Ed (TESOL Int) Penguji 2

This study entitled “Difficulties in Using Modal Auxiliary to Express Polite Requests Encountered by the Twelfth-Grade Students in the Science Program of SMA Negeri 4 Kupang” investigates the difficulties in using modal auxiliary to express polite requests by identifying grammatical errors and the inappropriate modal auxiliary. Also, to find out the causes of the difficulties in using modal auxiliary to express polite requests. The sample of this study was class XII IPA 4 which consisted of 36 students of SMA Negeri 4 Kupang in the academic year 2022/2023. To conduct this study, the writer used the descriptive qualitative method. The result of this study shows that the students faced 2 difficulties in using modal auxiliary to express polite requests. First, they faced difficulties in forming sentences that caused grammatical errors. The total error made by the students is 123 errors. Those 123 errors consist of 52 errors of addition, 65 errors of omission, and 6 errors of misordering. Second, the students faced difficulties in applying the appropriate modal auxiliary to express polite. The causes of grammatical errors in using modal auxiliary to express polite requests made by the twelfth-grade students in the science program of SMA Negeri 4 Kupang in the academic year 2022/2023 are carelessness and translation. The cause of applying inappropriate modal auxiliary to express polite requests is the level of politeness of each modal auxiliary. Keywords: difficulties, modal auxiliary, polite request.