This study aims to find out about the morphological interference of Bahasa Mandailing to Bahasa Indoensia and its implication to the teaching speaking materials improvement of vii grade students of Madrasah Mardiyah Islamiyah (MTS MMI) Penyabungan II Mandailing Natal in narrative text. The research results can be known that in Bahasa Indonesia there is a morphological interference of the students’ Bahasa Mandailing to Bahasa Indonesian like the base word, affixation and reduplication. The research found the realization factor of morphological interference that is internal and external factors. The results of this study have implications for the development of teaching speaking materials in narrative text in the form of materials about narrative essay in which there is a morphology interference of Bahasa Mandailing in Bahasa Indonesia. The results of interview, morphological interference materials of Bahasa Mandailing into Bahasa Indonesia have relevant for the development of teaching speaking materials in narrative text to increase the knowledge about Bahasa Indonesia. The type of research is qualitative research. The method used is descriptive method that tries to describe a phenomenon or symptoms happen in real circumstances. The research data are words in sentences containing morphological interference of Bahasa Mandailing.
Keywords: Interference, Morphology, Speaking, Teaching Materials
