the lasting effect of the morphological instruction on the vocabulary gain of iranian efl students: the case of a rural school

This study was conducted to examine the long-term effect that morphological instruction can exert on the iranian efl learner’ vocabulary size. in order to fulfill this goal, 60 eleventh-grade students were selected based on available sampling procedures from a senior high school in varamin, tehran. they were assessed in terms of their language proficiency and vocabulary knowledge through administering a vocabulary level test. then, they were divided into an experimental and comparison group. the experimental group received the morphological instruction and the comparison group was given translation. immediately after finishing 8-session treatment, a parallel form of initial vocabulary pretest was administered as the posttest and after a two-week interval, the same test was given to the participants as the first delayed posttest. finally, after a month interval, the second delayed posttest was administered to further examine the strength of the effect of the treatment. the obtained results, analyzed through repeated-measure analysis of covariance suggested that incorporating morphological instruction in the process of vocabulary learning has a long-term influence on the efl learners’ vocabulary gain.