Language shift is the process by which a speech community transitions from primarily using one language to predominantly using another over time. As a central concept within sociolinguistics, it investigates the complex socio-historical, demographic, and communicative factors that drive the gradual decline in the use of a heritage language and its eventual replacement by a dominant language within a community or population group, examining patterns of intergenerational language transmission, social pressure, and economic influence. Its significance lies in providing a framework for analyzing language change, linguistic vitality, and the social dynamics underlying language maintenance and loss.