Error analysis is considered as an invaluable pedagogical tool in teaching English as a foreign/second language (EFL/ESL). Despite abundant research, there are still lacunae in studies investigating the written grammatical errors among monolingual and bilingual male and female Persian and Turkmen EFL learners. To fill the gap, 158 Persian and Turkmen EFL learners from Golestan Province wrote two descriptive scripts that were examined for their most recurrent written grammatical errors. The errors were then analyzed and compared based on the framework of the study. Statistical analyses indicated significant relationships between Persian and Turkmens’ written grammatical errors and their gender. The frequency of monolingual Persians’ errors was significantly lower than that of bilingual Turkmens. These findings might interest EFL teachers, syllabus designers, and materials developers. Moreover, they could be a prerequisite to corrective feedback research while opening doors to further pertinent studies. Manuscript profile

Errors are one of the enigmatic parts in the process of foreign language (L2) learning as they are extremely versatile at each and every stage of the language learning proficiency. The present study, therefore, was an attempt to reveal Iranian EFL learners’ grammatical errors in writing at two levels of proficiency, namely lower intermediate and advanced, and then to investigate whether there was a relationship between the levels of EFL learners’ proficiency and the types of grammatical errors they committed in their scripts. The study was carried out at a private language institute in Gorgan, Iran. To this end, 60 female EFL learners (30 lower intermediate and 30 advanced females) whose age ranged between 13 and 17 participated in this study and wrote 150 word writing samples on a predetermined descriptive subject. The descriptive analyses of the data based on the scoring framework of the study demonstrated the types of grammatical errors at each level of proficiency. A Chi Square test was then run in SPSS Ver. 25 on the 16 common frequent error categories between both levels of proficiency, which verified the existence of a relationship between EFL learners’ levels of proficiency and the types of written grammatical errors they committed in their writing. The findings of the study might be of interest to EFL learners, EFL teachers, syllabus designers, and materials developers. Manuscript profile