Mariethe M. A. Pello Pengarang YANPITHERZON LIUNOKAS Dosen Pembimbing 1 Gupuh Rahayu Dosen Pembimbing 2 Yanpitherzon Liunokas Penguji 1 Marcelinus Akoli Ketua Penguji Gupuh Rahayu Penguji 2

This thesis is entitled: ‘Grammatical Errors Committed by Eleventh Grade Students of SMAK Sint Carolus Kupang in Academic Year 2023/2024 in Writing Descriptive Text’. This thesis investigates two main research questions (1) What are types of grammatical errors committed by eleventh grade students of SMAK Sint Carolus Kupang in academic year 2023/2024 in writing a descriptive text? (2) What are the possible causes of those errors in writing a descriptive text committed by eleventh grade students of SMAK Sint Carolus Kupang? The study aims to identify and describe the types of grammatical errors made by the students and the causes of those errors in their descriptive texts. This study was conducted using descriptive qualitative research method and was held in SMAK Sint Carolus Kupang, from January to February, 2024. The subject of this study is the eleventh grade students of SMAK Sint Carolus Kupang in the academic year 2023/2024, which consists of 63 students. The researcher collected the data in this study through students' descriptive texts and interviews. The researcher used the error analysis method by referring to Dulay's surface strategy taxonomy regarding the types of error and Norrish's theory regarding the cause of error. The results show that the types of errors found in the students' descriptive text are 54 omission errors (40%), 18 errors additions (13%), 49 misformation errors (37%), and 13 errors of misordering (10%). The causes of error found in this research were carelessness, first-language interference, and translation. Hence, an engaging learning style from the teacher and mastery of grammar also vocabulary with lots of practice are needed to help students develop writing skills in the future. Keywords: Grammatical Error, Descriptive Text, Writing.