Abstrak
ABSTRACT VIANI SEPTIANDARI, 2313.033. Students’ Ability in Using Suffix in Vocabulary Idiom of the Fifth Semester Students of English Education Department at IAIN Bukittinggi in Academic 2017/2018. Thesis, State Islamic Institute Bukittinggi (IAIN). The research was done because the researcher found several problems were faced by fifth semester students of English Education Department at IAIN Bukittinggi in using suffix in vocabulary idioms. Based on preliminary research, the researcher found the students vocabulary were lacking and got confused in placement of suffix, they did not pay attention for function of nouns and verb forms. Thus, the researcher conducted the research in order to know what students ability in vocabulary espsecially suffix is. The design of this research is a descriptive research with descriptive quantitative research. The sample is fifth semester students of English Education Department at IAIN Bukittinggi which consist 128 students. The sample was choosing by using random sampling. The research was conducted in November 13st to Desember 30st 2017. The research data were collected by using multiple choice test. It contains 26 items. The result of analysis shows that the students’ ability in using suffix was “poor” with total score was 59.31. For the types of suffix the researcher found the students’ ability in using suffix of noun-forming was at poor level because its means’ score was 56.73. Futhermore, the students’ ability in using suffix of verb-forming was “very poor” level because its means’ score was 46.15. While, the students’ ability in using suffix of adverb-forming was “fair level” because its means’ score core was 65.38. Also, the students’ ability in using suffix of adjective-forming was “very poor” level because its means’s score was 69.23. So, it can be concluded that the ability of fifth semester students of English Education Department at IAIN Bukittinggi in using suffix is “poor” level.