Ragil Afriansah Y Pengarang SANTRI EMILIN PINGSABOI DJAHIMO Dosen Pembimbing 2 Laurensius Kian Bera, Dosen Pembimbing 1 Santri Emilin Pingsaboi Djahimo Penguji 1 Elisna Huan Penguji 2 Laurensius Kian Bera Ketua Penguji

This research aimed to analyse the grammatical errors committed by debaters in debating competition in their speech in debating competition held by the Faculty of Teacher Training and Education, the University of Nusa Cendana, from 25 to 27 July 2020. The found errors were counted and presented in frequencies and percentages, and ranks. Then, the writer employed the research findings to determine the factors or reason why they commit such errors.Referring to research question 1, “What grammatical errors are mostly committed by debaters?” the findings show that there were 132 errors found in their speech. The frequency of errors could be separated into 3 (2.27%) interlingual error and 129 (97.72%) intralingual errors. According to the research findings, the errors found in the intralingual errors were greater than the interlingual errors. It could show that the debaters had encountered more difficulties in English grammar. It meant that the debaters had many problems in the usage of grammatical rules when delivering a speech. This result was in line with Silalahi (2013) previous study about Common Grammatical Errors in Spoken English of University Students in an IT University. The top three of the most frequent error committed by debaters in this research were pronunciations (88%), tenses (63%), and loss of meaning (63%). It meant that the debaters needed to focus much more on grammatical rules when delivering a speech, especially pronunciations, tenses, and loss of meaning.Referring to research question 2, “Why do they commit such errors?” the findings show three main reasons why they commit such errors: lack of confidence, critical thinking, and lack of knowledge. It could show that the debaters had encountered more difficulties when delivering speech because they are not confident, have a low critical thinking level and lack grammar knowledge. Keyowrds: Debating, Debaters, Grammatical Errors, Interlingual, Intralingual