Abstrak
This research aimed to investigate errors in the use of grammatical cohesive devices based on Hasan and Halliday’s theory. The study focused on identifying the types of errors and most frequent categories of errors in grammatical cohesion in analytical exposition texts written by eleventh-grade students at SMAN 1 Tilatang Kamang. This research conducted due to some problems arose and reasonable to be identified were students still facing the difficulty to develop their arguments into good sentences and lack of grammar and ability to write. Data was collected from 35 students' assignments on topics provided by the teacher. A qualitative approach was used for data analysis. The results indicated that learners made errors in reference, conjunction, and substitution. Specifically, 67% of the errors were in reference, 32% in conjunction, and 1% in substitution. Although errors in substitution were infrequent and none were found in ellipsis, this does not mean students never faced issues with these categories. Instead, it suggests that students might have avoided these complex categories or that written language employs these cohesive devices more frequently than spoken discourse.