2.Literature review

This chapter gives a detailed introduction of previous studies in the field with which this study is closely linked. It starts with definitions and concepts of some important terms related to vocabulary knowledge. After that, previous researches on vocabulary and reading comprehension are introduced. At the end of this part, the research gap is discussed.

2.1 Definitions

Many people define vocabulary in many ways, it is generally accepted that knowing a word is not limited to its dictionary definition or what it looks or sounds like. From a theoretical perspective vocabulary knowledge is a multidimensional and multi-faceted construct (Read, 2000). Three dimensions within the construct are accepted by and large,which can be defined as: vocabulary breadth (or vocabulary size), vocabulary depth and vocabulary fluency (Daller et al., 2007; Milton, 2013). According to Saeed Mehrpour and Mohammad Rahimi(2010), general knowledge of vocabulary means frequently used words in English, and by specific knowledge of vocabulary means knowledge of less frequently used words or technical and difficult words appearing in a text.

2.2 Vocabulary and reading

Many researches have been conducted to investigate the relationship between vocabulary and reading . Grabe (1991), for instance, considered vocabulary knowledge as the prime predictor of reading ability. In the same way, Coady et al. (1993) conducted two experiments that showed that increased proficiency in highly used vocabulary also led to an increase in reading proficiency. There are also numerous studies that provide empirical estimation of the number of words learners need to know in order to effectively handle the text and comprehend it. For example, Grabe (1991), as cited in Butler-Pascoe amp; Wiburg (2003) argues that, ”#8230;fluent L2/FL readers need to know about 2,000 to 7,000 words and sometimes even more if they want to reach native-like fluency”. Constantinescu (2007, p.2) holds that L2/FL readers need to recognize approximately 95 per cent of the words in a given text in order to comprehend its meaning and they need to know the different meanings of words according to context, as well as words' grammatical properties. While Alderson (2000) raised a question whether reading is a problem of language or a problem of reading. He pointed out that in the early stage of language learning, language played an important role in the comprehension. In other words, language, which is the key point, prevents people from understanding the whole passage.

2.3 Research gap

As we can see all these researches mainly deal with the relationship between general knowledge of vocabulary and reading comprehension. The truth is the specific vocabulary as well as the general knowledge of vocabulary should be researched together in reading comprehension. This research intends to study this two elements at the same time, which can fill the research gap of the previous researches.