INTRODUCTION
After many decades of being neglect and receiving little importance, teaching and learning second language (L2) vocabulary has now markedly become into the focus of interest of many applied linguistic researchers and language teachers (Barcroft, 2004; Decaricco, 2001; Read, 2000). Moreover, lexical competence is currently acknowledged to be a core component of communicative competence by many vocabulary specialists, which provides much of the basis for how well learners speak, listen, read and write (Coady & Huckin, 1997; Richards & Renandya, 2002). In the past, it was thought that vocabulary could simply be learned effortlessly, and received only incidental attention in many textbooks and language programs. However, mastering vocabulary is one of the most challenging tasks that any learner faces when learning a foreign language and, thus, many language learners devote a great deal of time on memorizing lists of L2 words and rely on their bilingual dictionary as a basic communicative resource; furthermore, they consider L2 acquisition as essentially a matter of learning vocabulary.