Cameron (2001) defined vocabulary learning strategies as the actions that learners take to help themselves understand and remember vocabulary items. Catalan (2003) stated that knowledge about the mechanisms (processes, strategies) used in order to learn vocabulary as well as steps or actions taken by students (a) to find out the meaning of unknown words, (b) to retain them in long-term memory, (c) to recall them at will, and (d) to use them in oral or written mode. In addition, Intaraprasert (2004) mentioned that any set of techniques or learning behaviors, which language learners reported using in order to discover the meaning of a new word, to retain the knowledge of newly-learned words, and to expand their knowledge of vocabulary.