Vocabulary can be a key factor for success, central to a language, and paramount to a language learner. In such situation, the lexicon may be the most important component for learners (Grass and Selinker, 1994), and mastering of vocabulary is an essential component of second/foreign language teaching and learning that has been repeatedly acknowledged in theoretical and empirical second/foreign language acquisition research. The intent of the current study is to set out the nature of vocabulary acquisition alongside the expressing importance of vocabulary acquisition. The importance of the present study is to explore the current studies of vocabulary in order to find out common main gaps among such studies.