This study focuses on language change, specifically the lexical change of the Batak Toba language in two different areas. This research aims to contribute to other researchers and governments related to the future of the local language in maintaining the local language itself. This research used a qualitative research method, specifically a case study, to analyze language aspects among people who use the Batak Toba language in their area. Miles and Huberman’s technique of collecting data was used in this research. The data was collected from two different Batak Language videos in two different areas. The video was transcripted and eliminated by identifying synonyms and homonyms using language change theories. The online Batak dictionary was used to verify the meaning of every synonym and homonym itself. From the data source, which is 25 (twenty-five) videos, the total of the synonym is 22 words, with the detail 14 words found through videos in Tapanuli Tengah and eight words found through Humbang Hasundutan. Similarly, the homonym between these two districts can also be found, with 3 (three) homonyms. Lexical change through synonyms and homonyms occurs because of convergence, cultural change, and lexical borrowing, second language learning, and relexification.
Keywords: homonym, language change, synonym