摘要:The purpose of this study was to explore the function of English restrictive and non-restrictive relative clauses in discourse cohesion and also intended to examine the possible differences between comprehension and production of restrictive relative clauses and non-restrictive relative clauses and their sub-types. Centering Theory was adopted as a framework to evaluate the coherence of discourse. To this end, 200 Iranian EFL language learners (112 females and 88 males) majoring in English as a foreign language, selected based on convenience sampling from Marvdasht and Shiraz Islamic Azad universities. They did two researcher-made tests, namely a 20-item reading comprehension test and a writing test. The reading comprehension test required the participants to read sentences containing a main and subordinate relative clause and choose the correct choice from 3 proposed answers. Likewise, to analyze their writing and productions in terms of relative clauses, the participants were asked to read 20 sentences consisting of a main clause followed by a blank in which they needed to create a sentence using a relative clause. algorithm was utilized to analyze the data. The results suggested that the participants understood and produced restrictive relative clauses better than non-restrictive relative clauses. Moreover, Identifying restrictive relative clauses and Continuative non-restrictive relative clauses were understood and produced better than Classifying restrictive relative clauses, Subjectivity, and Relevance non-restrictive relative clauses, respectively. The results of this study carry crucial pedagogical implications for teachers, language learners, and syllabus designers.