Abstract This study investigates errors in Indonesian language writing among university students, focusing on their types, frequency, and underlying causes. Employing a qualitative case study design, the research analyzed 30 essays written by second-year undergraduates and conducted semi-structured interviews with a subset of participants. Errors were classified using both the surface strategy taxonomy (omission, addition, misformation, and misordering) and linguistic categories (morphological, syntactic, lexical, and discourse). A total of 1,427 errors were identified, with misformation (42.2%) and omission (35.9%) being the most frequent types. Syntactic errors (38.6%) and morphological errors (33.2%) dominated at the linguistic level, reflecting students’ challenges in sentence construction and affixation. Lexical errors, while less frequent, often resulted in inappropriate or awkward word choices, whereas discourse errors revealed weak cohesion and coherence. Interview data highlighted the influence of local languages, overreliance on spoken Indonesian, and limited exposure to academic writing conventions as key contributors to these errors. The findings demonstrate that errors are not random but systematic indicators of interlanguage development. Pedagogically, the study underscores the need for explicit instruction in affixation, sentence structure, academic vocabulary, and discourse organization. It also advocates for error analysis as a diagnostic tool for teachers, allowing them to design remedial strategies tailored to learners’ specific needs. By combining descriptive data with explanatory insights, this research enriches the understanding of Indonesian writing difficulties and offers practical implications for improving writing pedagogy in higher education.
Maria Ulviani (Mon,) studied this question.