Idioms give beauty to language and headache to language learners. Different techniques have been offered to facilitate L2 learners' acquisition of idioms. There are also various factors that influence the learning of idiomatic expressions. This book focuses on three of the most important factors, etymological elaboration, contextual pragmatic clues, and lexical Knowledge. The effects of these factors are empirically investigated, and results are presented in tables and figures. The findings of this study may have theoretical as well as practical implications for teachers and course designers.