The root of a language is vocabulary. Without an adequate vocabulary, you cannot describe your thoughts and feelings. Stahl (2005) defines vocabulary as knowledge of a word that not only involves a definition, but also involves how words fit into the world. This is further supported by Qing Ma (2009) stating that knowing the meaning of words and how to use it appropriately in different contexts is called vocabulary. There is no denying that vocabulary plays an important role in determining one's language proficiency because vocabulary is the core of language skills. In general, students have difficulty expressing their thoughts and feelings due to their inadequate vocabulary. This problem is quite common among second language learners. Anderson and Freebody (1981) in Baumann (2005) wrote that reading comprehension and vocabulary shared a strong link that was recognized 80 years ago. Ediger (1999) to Donohue (2000) in his research found that insufficient knowledge of functional vocabulary is one of the reasons why students do not read well. Donohue (2000) states that it is necessary for students to have prior knowledge of the topic to ensure understanding. The strong link between students' prior knowledge and the topic covered affects students' ability to understand a text. Kasper (2000), in Bourn (2012) stated that this theory was founded on the basis of communication between students' background knowledge and texts which results in understanding. This can be confirmed by the study conducted by Liu Na (1985). Liu Na found that students should cover 95% of the text. Students' familiarity with the topic also influences their difficulty in...... half of the paper Benjamin (2009). The purpose of this research is to enrich students' vocabulary using contextual clues. By mastering the skill of contextual clues, students would not need to depend on a dictionary or other sources to find the meaning of unknown words. Students become disinterested in the text if they need to consult the dictionary every time they encounter difficult words. Educators can also benefit from this research where they will be exposed to various types of contextual clues where they can use them to expand students' vocabulary. 1.3 Purpose of the research This study aims to find the degree of use of contextual clues in improving students' vocabulary. Besides that, this study also aimed to find out what types of contextual clues students are most familiar with and finally students' reaction when encountering unfamiliar words in a text.