This chapter describes the background of the study, the research problem, the purposes of the study, the significances of the study, the scope of the study, and the definition of key terms.
1.1 The Background of the Study In learning language, one of language components that should be mastered by learners is vocabulary. The learners should master vocabulary in order to be able to communicate in the target language and help the learners to understand and use the language easily. Troike (2006: 138) states that vocabulary (or lexicon) is the most important level of L2 knowledge for all learners to develop–whether they are aiming primarily for either academic or interpersonal competence or a broader scope of communicative competence that spans two. Vocabulary is also important in the process of teaching and learning language because it supports the learner’s ability in language skills. The learners should master vocabulary well if they want to have better language skills. Huyen and Nga (2003), Zhao (2009), and Cahyono and Widiati (2011) agree that the mastery of vocabulary plays a key role in the whole process of second language learning and is of critical importance to the learners. Without a solid mastery of vocabulary, listening, reading, translation, and writing are all attics in the air. So, vocabulary is one that links four skills.
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2 The learners are not able to communicate well with each other in the foreign language if they have low vocabulary mastery. They can not express their idea briefly because they do not have enough vocabulary. Akbari (2008) states that speakers cannot convey meaning and communicate with each other in a particular language. Moreover, Moras (2001) states that students need to broaden their vocabulary to express themselves more clearly and appropriately in wide range of situations. Vocabulary is important to be mastered by language learners, especially English learners, because English vocabulary is