This study was an attempt to examine whether the Iranian EFL learners’ use of contextual clues has any significant impact on their knowledge of unknown vocabularies. The participants of the study were one hundred Iranian elementary, intermediate, advanced learners of Andishe Bartar institute in Iran. To homogenize the participants in terms of their English Language Cambridge tests was run sixty participants whose scores fell one standard deviation above and below the mean were selected to take part in the study. The participants were randomly divided into three groups. Firstly, three groups were given pre- tests as experimental groups. After that, four types of contextual clue – explanation, example, antonym, synonym- were taught and practiced during ten sessions of instructions. After teaching, other tests of English Cambridge tests were administered as a post test. The analysis of data revealed that knowledge and use of contextual clues has a significant impact on guessing the meaning of unknown vocabularies amongst three groups.
Keywords: Explanation, antonym, example, prediction of meaning, synonym, types of contextual clues, unknown vocabularies
