The Use of Code Mixing by English Teachers at Mts Negeri 2 Deli Serdang.Thesis.Faculty of Tarbiyah and Teachers Training. State Islamic University of North Sumatera Medan 2019.

This research aimed to investigate the use of code mixing by English teachers at MTs Negeri 2 Deli Serdang. This study aims 1) to show the types of code mixing used by the English teachers in the teaching and learning process and type of code mixing that is most frequently used by English teachers. 2) to describe the reasons why the teachers at MTs Negeri 2 Deli Serdang used code mixing. 3) to describe the students' understanding of the use of code mixing by English teachers. The data were analyzed by using qualitative methods. The data were taken from the observation, interview with the teacher and collected the students’ score test to obtain the data regarding students' understanding toward code mixing. The data were analyzed based on the types of code mixing by Hoffman's theory namely: intra sentential code mixing, intra lexical code mixing, and involving a change of pronunciation. The English teachers of MTs Negeri 2 Deli Serdang except teacher 1 used the three types of code mixing. Teacher 1 only used two types of code mixing namely intra sentential code mixing and involving a change of pronunciation. All of the teachers of MTs Negeri 2 Deli Serdang most frequently used intra-sentential code mixing in the teaching and learning process. The reasons for the teachers used code mixing in teaching and learning process were to make students more understand what is said or instructed by the teacher and understand the material explained. The students at MTs Negeri 2 Deli Serdang could understand English lessons taught by teachers by using code mixing which could be seen from the results of their tests which half of the students succesfully reached KKM