Historical linguistics is the study of how languages change over time, including their evolution, relationships, and development. This field examines the historical origins, development, and relationships among languages, as well as the processes of language change such as sound changes, semantic shifts, and grammatical changes. Historical linguistics also investigates the reconstruction of proto-languages, or hypothetical common ancestors from which modern languages are descended. This research area provides insight into the history of human language and how languages have evolved and diversified over thousands of years.