ELS Journal on Interdisciplinary Studies in Humanities Volume 4 Issue 1, 2021 DOI: https://doi.org/10.34050/elsjish.v4i1.12747 Homepage: journal.unhas.ac.id/index.php/jish 41 Grammatical Errors in English Informal Essays by The Sixth Semester of English Literature Students Jumardin Muchtar 1* , Dahniar 1 , Nur Mutmainnah Halim 1 1 English Literature Department, Literature and Humanity Faculty, Universitas Islam Makassar, Indonesia *Correspondence: jumardinmuchtar025@gmail.com ABSTRACT ARTICLE HISTORY Published March 27 th 2021 KEYWORDS Error, Grammatical, Informal Essays ARTICLE LICENCE © 2021 Universitas Hasanuddin Under the license CC BY-SA 4.0 This research focused on Dulay's and Richard's theories about grammatical errors. This research purposed to (1) describe grammatical error types in English informal essay were made by the sixth semester of English Literature students in Makassar Islamic University and (2) find grammatical error causes in the informal essay were made by the sixth semester of English Literature students in Makassar Islamic University. The researcher used qualitative methods to analyze the types of errors in students' questionnaires and essays based on Dulay's theory: omission, Addition, mis formation, and disordering. Meanwhile, the researcher also found error causes by Richard's theory, namely, interference, overgeneralization, ignorance of the rule restriction, incomplete rule restriction, and false concept hypothesized. This research demonstrated 210 errors in students' questionnaires and essays. First, fifty-two errors in omission: twenty-nine errors in the omission of the auxiliary verb, three errors in the omission of the ordinary verb, six errors omission of the noun, eight errors in the omission of a plural noun, two errors in the omission of gerund noun and four errors in the omission of the preposition. Second, ninety-three errors, in Addition, those were: twelve errors in double marking, fifty-one errors in regularization, and thirty errors in simple Addition. Third, fifty-one errors in misinformation last were fourteen errors in disordering, which were found in interference, overgeneralization, ignorance of the rule restriction, incomplete rule restriction, and false concept hypothesized. 1. Introduction Language is a medium of communication to acquire the information (Rahman & Letlora, 2018). The language is a communication tool to express the idea and feeling to those invited to talk. The transmission and reception of thought and feeling arisen during the communication process needs language to endorse the effectiveness (Suherman, 2018). As we know, language communication began when people thought of something that was in their minds. People tried to express it through their mouth by using words, phrases, and sentences. On the other hand, interlocutors tried to understand other's speech so that their communication runs smoothly. English as an international language has become the most widely studied in the world (Riski, et al., 2018; Weda, et al., 2021). Learning English as a foreign language poses a challenging aspect for students and lecturers, particularly in Indonesia (Rahman, 2018). In the language process, English in particular, we must know some language skills. There were at least four skills that we had to master. They were listening, speaking, reading, and writing. Not only English but also other foreign languages needed these skills. Without these skills, the human would never be able to communicate with each other. These four skills were the main tools when we expressed something that we meant it. However, those skills could be classified into two characteristics: receptive and productive skills. Receptive skills were listening and reading skills, which students required to know the language, both verbal and written. It aims to understand pronunciation, master audio listening practice, and find new vocabulary, whereas productive skills were taken by someone to produce languages such as speaking and writing skills. It was usually more difficult than other skills because a person must work both oral and significantly in writing.