Vocabulary knowledge plays a crucial role in academic development and therefore scholastic success (National Reading Panel, 2000). Also, students' vocabulary knowledge expands through a variety of ways. One of the most practicable strategies in vocabulary learning supported by many researchers is using affix knowledge. The purpose of present study is to investigate the effect of morphological instructions on vocabulary learning among Iranian secondary school students. Participants in this study were sixty Iranian secondary school students who were assigned to control group (30) and experimental group (30). A pre-test and post-test comprising two vocabulary tests measuring students' morphemic analysis of general English words were administered. The data were analyzed using the Independent Sample T-test to determine if there were improvements made in the two measures within each group, and subsequently whether the magnitude of improvement between the two groups were significant. The results indicated that the experimental group outperformed the control group in the process of guessing the meanings of complex words depending on the morphological analysis. Furthermore, the results did not show significant differences between Morphological Relatedness Strategy and Morphological Structure Strategy in terms of students' achievements.

Bilingualism can be broadly defined as the ability to speak two languages; however, there are many grey areas when establishing which are the first language, the second language, and the third language of a bilingual. The paper reports on a study exploring the effect of bilingualism on the learning of a vocabulary learning of two groups of Iranian male students: Baluchi bilinguals and Persian monolingual. The present study is based on the data from 80 monolingual Persian-speaking learners of English and 80 bilingual Baluchi-Persian-speaking learners of English. All participants were male studying English as a foreign language at pre-university of Sistan and Baluchestan in Iran. The results indicated that Baluchi-Persian bilingual speakers outperformed in general vocabulary learning and inL3 recognition vocabulary learning. The findings of this paper also showed that no significant difference was seen between Persian-speaking learners and Baluchi-Persian-speaking in L3 production vocabulary learning (p˃.05).