The aim of this study was to develop the application of English Vocabulary Application based on the desktop version to assist the mentally-retarded students in learning English vocabulary. This research used Research and Development (R&D) with ADDIE models. This research involved 5 seventh-grader of mentally-retarded students and 3 teachers who teach mentally-retarded students from SLB Arya Satya Hati. The researcher used three instruments for this research: (1) Interview,
(2) Questionnaire, and (3) Documentation. The data were analyzed by using Arikunto’s theory (2010) and percentage index (%). The researcher carried out the dissemination by uploading the video on how to operate the English Vocabulary Application on Youtube due to the COVID-19 pandemic. From the validation results, it showed that English Vocabulary Application was feasible to be used as a learning media in assisting the mentally-retarded students with 100% materials validation results and 95% programming validation results. Based on the application try-out, 4 MR students could guess more than 10 words of 20 words and 1 MR student guessed 8 words of 20 words. Based on this research, the English Vocabulary Application could be used in teaching- learning vocabulary for mentally-retarded students through ICT. This application could be used as one ICT learning media and the other researcher could develop this application with the newest features.
Keywords: English Vocabulary Application, Mentally-Retarded students, teaching vocabulary