<![CDATA[Indonesia is a unitary country that has a diversity of ethnicities, races, religions, and languages, with Indonesian as the national language and a unifying tool. In its development, the use of Indonesian language often experiences code mixing and language interference, especially in the Papua region such as Sorong City which has high linguistic complexity. From a linguistic point of view, this region shows a variety of typologies and language clusters, so this study focuses on the interference of the local dialect of Sorong on the use of oral formal Indonesian in students of Muhammadiyah Al-Amin High School. The research aims to analyze and identify these forms of interference. The research uses a qualitative approach with a descriptive method to describe the linguistic phenomena that occur. Data was collected through field observations, recordings, field notes, and interviews with subject teachers. The focus of the study is the use of a mixture of regional language and Indonesian vocabulary that appear simultaneously in student communication. The results of the study show that there is a phenomenon of language mixing with the discovery of fifty-five regional vocabulary used in Indonesian conversations. This interference gives rise to linguistic variations in phonology, morphology, lexical, syntactic, and semantic aspects as students interact in class. These findings show the importance of developing a language curriculum that emphasizes a balance between mastery of regional languages and Indonesian through an educational approach.]]>
