Morphological complexity is one of the dimensions of complexity that has been increasingly analyzed over the last few years. However, results from previous studies drawing on only a single text type are inconclusive. The purpose of this study was to determine the effect of text types (descriptive, narrative, and expository) on the morphological complexity of essays written by Iranian English language learners. The participants included 87 lower-intermediate male and female L2 learners at six language institutes in Qazvin, Iran, who were selected from 127 language learners taking an Oxford Quick Placement test. The participants wrote on each text type in three consecutive weeks as a part of their classroom activity. The morphological complexity of verbs and nouns was separately calculated using the morphological complexity index. The data were analyzed using a series of Friedman and Wilcoxon Signed Rank Tests. The findings did not show any statistically significant differences across text types for nominal inflectional diversity; however, verbal inflectional diversity was statistically significant across text types, with narrative essays morphologically more complex than descriptive and expository essays. The findings may have theoretical and pedagogical implications for researchers and L2 teachers.
